If I CA coat wooden scales, I usually degrease the wood surface by using some household ammonia on a piece of cloth. Works perfectly fine with many types of wood.
Do not do this with purple heart.
:(
Luckily, I tried the insides first.
I found that the top layer of the wood developed a greenish slimy muck when touched by ammonia. I managed to wipe off most of it, and when it dried it was not too bad. But on the outsides it really would have damaged the scales.
