Right forum for the question.
How long have you let the stuff dry? I thought I read a post recently where someone suggested that a heavy coat might take a dya or two to fully dry, remaining somewhat milky until it has.
If you do definitely have to remove it, is Pollys flat acrylic? If so, try some alchol. I've used alcohol remove Future after drying. If that fails, may windex. I'm thinking that something like turpentine might be rather drastic and clobber your whole paint job (I mad a wash with it only to have it start lifting the paint underneath), so I'm thinking you want to start with the lightest stuff first.