One thing I would highly suggest is to wrap the handle in some kind of app tape. The app tape does two things for the engraving process. 1. It shields the wood from smoke residue. 2. It also helps when doing the paint fill because it works like a mask. Similar to when you paint a room in the house the tape helps so that you don't get unwanted paint on places it should not be in.
Of course these type jobs are a bit nerve racking but if you do your research and take your time its no trouble at all.