blueman wrote:
We have some old dark staind wainscoating in one of our bathrooms.
I would like to clean it up and put on a protective coat of poly.

I'm not sure what the old finish is, but I was thinking of doing the
following:
1. Cleaning it with alcahol or mineral spirits?
(I know if the old finish was shellac, then alcahol would tend to
dissolve it)
2. Cover it with a couple of applications of oil-based wipe-on satin
polyurethane

Is this a good idea?
If so, anything to add to my approach?
If not, any suggestions on a better approach?

If possible, I would like to avoid a major project of stripping off the
old finish and staining and starting from scratch...

If the old finish was shellac, you probably would have had water spots
(white) on it by now. I would clean it first with cool water and
detergent - I do the same with good furniture - which will not harm the
wood if you don't saturate it and leave it wet. Bathrooms don't get
greasy like a kitchen, so I would not be inclined to use m.s. I do use
m.s. to remove wax and greasy dirt. Let it dry well. If the finish is
glossy, rub it down with fine steel wool prior to clear coat. Vacuum
dust very well.