I've just reviewed the thread and here are a couple of thoughts.

1. Most of the HP ratings you see on retail compressors are "Peak" which
is more a measure of the inertia in the motor than a true measure of its
power. A motor converts electrical power to mechanical. The maximum
electrical power you can get out of a regular outlet is ( if I remember
correctly ) about 1.25 HP. Even assuming 100% efficiency ( breaks 3rd
law of thermodynamics) you can't have a motor with more than about 1.25
continuous power on a 110V 15A circuit, anything greater is the
marketing department skirting the edge of lying.

2. The ratings that you are interested in is the CFM ( cubic feet per
minute) at a particular PSI ( pounds per square inch). All the tools
have a minmum rating with the same numbers I.E. 8 CFM at 80 PSI. If the
compressor's CFM is less than the sum of the CFMs of the tools you use
at the SAME time then you will have problems having to wait for the
compressor to fill the tank. You need to convert to the same pressure.

I.E. Two tools

a. 6 CFM at 60 PSI; and
b. 8 CFM at 120 PSI.

equals

a. 3CFM at 120 PSI; and
b. 8CFM at 120 PSI

Total 11 CFM at 120 PSI

If your compressor is rated at less than that then you either use fewer
tools or get a bigger compressor.

3. You can get away with adding in a larger tank as long as its big
enough and your aveage usage is small enough. Essentially your letting
your compressor run for a long time and then using the air relatively
quickly. If you then wait for a while the compressor may catch up. Your
compressor will take longer to come up to working pressure and wear out
faster ( longer duty cycles). Personally I don't think its a good way to
go. I use my compressor infrequently but when I do I use it a lot all at
once.

4. If you are going to spray you need to get a water separator to get
the moisture out.

5. If you are going to use tools you either remember to put a drop of
oil in the tool regularly or you get an oiler which adds it to the air.

6. If your doing both 4 and 5 you need to have two separate MARKED hoses
since oil in the tool hose is bad for the paint gun. The best idea here
is to put the dryer in and then a T junction. One leg leads to the oiler
and then a quick connect for the "oiled" line. The other leg goes to a
quick connect for your paint line. Don't mix up the hoses or the "clean"
hose will be contaminated with oil.

7. For spray painting I have two HVLP setups. One is a 110V compressor
that is too small for anything but light usage, 5ft of one side of a 2x6
and you wait about 30 seconds for more air. The other is a 4 stage
turbine that works great. The turbine runs on a regular electrical
outlet, supplies lots of low pressure air and is easily portable. A
compressor based setup would require a trailer, 220V, gas or diesel
power to give the same portable performance. One the other hand I would
have to use a hammer if I didn't have the compressor.

HVLP = High Volume Low Pressure

Transfer Efficiency is up to double a regular gun and 75-80% of a brush.

TE is basically how much paint started out in the can as compared to how
much made it to the object being painted. A brush is close to 100%, HVLP
60-80%, regular high pressure spray gun is 30-40%, high pressure paint
pumps are worse than regular spray guns.

TTFN - Frank