How do you make sure the wood is flush with metal parts like the butt plate and tang?
Sand the wood and the adjoining metal part together so they wear down evenly at the same time, working the surrounding area rather than just one spot, since making just one small area flush without blending it into the surrounding wood will leave inconsistencies. Key areas to check are the top and sides of the butt plate where the tang is inlet, the ramrod entry pipe, and the trigger plate.