Robert:

I think I found out why the Easy Off window cleaner worked well for touching up dry paint, and I've got a guess as to what that "cottage cheese" stuff was.
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1. What was in that window cleaner that made it work well on latex paint?

I think Easy Off Window Cleaner is still available as Easy Off Glass Cleaner. I think they just changed the name.

I downloaded the MSDS sheet for Easy Off GLASS Cleaner (rather than Easy Off Window Cleaner):

http://www.rbnainfo.com/MSDS/US/Prof...US-English.pdf

and it's got a solvent commonly called PnB in it. The MSDS sheet says it has 2.5 to 10 percent PnB in it, 10 to 20 percent ethyl alcohol and the rest would be water (which doesn't have to be listed on the MSDS because it's not a potential safety hazard).

That MSDS sheet calls one of the constituents of the glass cleaner "2-Propanol, 1-butoxy-", but it also gives it's CAS number as 5131-66-8, and if you simply Google CAS 5131-66-8 you find out that it's a common industrial solvent called propylene glycol n-butyl ether, or PnB for short.

5131-66-8 | CAS DataBase

(There are different chemical naming conventions so a chemical can be called many different names, so the CAS system was developed to assign a numerical code to each chemical so that different kinds of scientists that use different naming conventions can all talk about the same chemical by just specifying it's Chemical Assay System, or CAS number. Google the CAS number and you find all of that chemical's aliases.)

All of the major chemical companies make PnB and sell it under their own trade names. Dow has Dowanol, Arco has Arcosol, BASF has Propasol, etc. If you can't find Easy Off GLASS Cleaner, then look under "Chemicals" in your yellow pages phone directory and phone around to find out who sells PnB in your area, and who they sell it to. The company that purchases it will hopefully give you some if you toss a $10 bill in that company's Christmas Party Fund. According to Google, Wal-Mart and Staples sell Easy Off Glass Cleaner.

The PnB is important because PnB is also used as a coalescing solvent in latex paints.

http://msdssearch.dow.com/PublishedL...romPage=GetDoc

So, spraying some PnB dissolved in water on dried latex paint would soften the paint, and allow it to self level again as the PnB and water evaporated.

(read the PS below to find out what PnB (or any coalescing solvent) does in a latex paint)

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2. What was that cottage cheeze stuff?

Next time, don't use any detergent when washing out your brush. What I'm thinking is that those blobs of cottage cheeze were the coalescing solvent in your primer/paint mixing with the detergent you used to clean the brush with.

Latex paints have water soluble coalescing solvents in them, and detergents are also soluble in water. Both are soluble in water only because one end of the solvent or detergent molecule is polar and is attracted to polar water molecules.

What I'm thinking is that the water soluble ends of the solvent molecules were attracted to the water soluble ends of the detergent molecules and the result was something that had the NON-water soluble ends of those molecules sticking out on both sides, thereby making stuff that was insoluble in water.

Maybe try buying a new (but inexpensive) paint brush (with no cottage cheeze in it to begin with) and paint something with that same primer/paint, and then wash the brush out thoroughly without using any detergent.

(I'm also presuming that this was softened water from your city's water supply system and not hard water from a well that you were using to clean the brush.)

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PS: Why do you need an industrial solvent in latex paint?

Welcome to Latex Paint 101:
Latex paints don't have any rubber tree sap in them.
Latex paints are a SLURRY (solids suspended in liquid) of tiny hard particles of clear plastic (called "binder resins"), coloured solid particles (called "coloured pigments") and white, clear or transluscent solid particles (called "extender pigments") suspended in a solution of a low volatility solvent (called a "coalescing solvent" or "coalescing agent") dissolved in water. So five things: three kinds of hard particles suspended in a solution of a solvent dissolved in water.
(There are also chemical additives in latex paints like mildewcides and defoamers, and but let's just ignore those. They don't play any roll in what the coalescing solvents do. )
When you spread latex paint on the wall, the first thing that happens is that the water evaporates, and the tiny plastic binder resins find themselves surrounded by that coalescing solvent at an ever increasing concentration. The coalescing solvent dissolves (kinda) those plastic binder resins, making them soft and sticky. The adhesion of the paint to the substrate occurs when the binder resins are soft and sticky.
The same force of surface tension that causes tiny droplets of water to coalesce into large rain drops in clowds then takes over and causes each soft sticky binder resin to stick to and pull on it's neighbors. The result is that all those tiny plastic resins "coalesce" to form a continuous soft film sticking to the substrate with the coloured and extender pigments suspended inside that film very much like the raisins in raisin bread. The coloured pigments give the paint film it's colour and the amount and coarseness of the extender pigments determine how rough or glossy the paint film dries to.
As the clear plastic binder resins coalesce into a solid continusous film, you no longer have gazillions of plastic/water interfaces (which previously reflected and refracted light like miniature prisms). Your eye sees light of all different colours as the colour "white", so as the clear binder resins coalesce to form a film, the amount of white light coming from the drying paint diminishes, and so the paint appears to darken as it dries. That is, latex paints darken as they dry for exactly the same reason that snow loses it's white colour as it melts to form water.
Then, the coalescing solvent evaporates from the paint film, filling the room with that freshly painted smell. And, as the coalescing solvent evaporates from the soft, sticky plastic film, that clear plastic hardens back up again to the same hardness as the original plastic binder resins were when the paint was still in the can.

In fact, most latex film formations will have several different coalescing solvents in them, each with a different evaporation rate. The reason for using a mix of solvents with different evaporation rates is to provide as wide a time window as possible for the water in the paint to evaporate. If the paint is being used on a humid day, that humidity will slow down the rate of water evaporation from the paint, but not the evaporation rate of the coalescing solvents. So, different kinds of coalescing solvents are used in latex paint, each with a faster or slower evaporation rate. That ensures that the coalescing solvent is always the last product to evaporate from the paint.