An old tried and true old world formula is a mixture of powdered washing soda(sodium carbonate) and a nice-smelling soft soap soap made from linseed oil that is made in the town of Mouscron ,Belgium by Savonneries G.Vandenputte.The product is called "mousse de lin " and has a gel like consistency.(The Belgians normally use the soft soap for cleaning their lovely unglazed red natural ceramic floor tile) Procedure : Thorughly mix the powdered washing soda and the soft soap in a suitable plastic container(use a stick or paddle) Apply the resulting goop to the painted surface and let it sit for 2 or three weeks .The product softens the paint and it can be easily removed with a water soaked rag . Not for peple in a hurry ,but safe and hassle free.If the paint is really thick you may need to apply again. Washing soda is mildly alkaline but not nearly as fierce as caustic soda.so it does not appear to harm thew wood substrate. But wear rubber gloves anyway as a precauton.