Yeah, organisol (vinyl paint) is not very "tough". Make SURE whatever cleaner you use it doesn't contain any chemical in it that ends in "one" (ketones, like acetone) since those will completely dissolve organisol paint pretty quick. Toluene/xylene/glycol ethers are pretty tough on organisols too. You might be stuck with hot soap & water....."maybe" some type of alcohol (isopropanol, ethanol) but be careful with those too and "test in an inconspicuous area first" just to be sure.