I am not sure about the alcohol test, but you could also do a test with acetone/ nail polish remover. That will soften and remove latex paints but not oil. If it is water based paint, and already not glossy, you could skip the sanding and just do a good cleaning before repainting with the latex satin impervo. ( or sand if you are trying to smooth stuff out.). But you are correct, if you are repainting old non glossy latex with new, you should not need to prime.

Please post on wavyglass.org. You'll get great old home advise there, true to your home.

This post was edited by jmc01 on Mon, Dec 8, 14 at 23:46

Thanks for confirming that coll.
jmc, I am familiar with wavyglass but wanted to post my question here. It is not an old house question but a painting trim question.