One more step, referring to your initial comment about smooth, crisp lines meeting the wood is to do any engraving and fine decorative filing AFTER the metal butt plate and wood are fully inlet. This is because the metal and wood surface are shaped in the final steps TOGETHER by the same file & abrasive action, in my experience. This continues, especially in the case of a butt plate tang typical of smooth bore & some rifled guns, with the use of abrasives such as emery & sand paper right down to a near polish. Then take off the butt plate, give a careful final polish being careful not to round the edges where the wood meets it, engrave & finish filing any raised moldings, and reinstall. Doing the finish work BEFORE the inletting & mating of the metal and wood surface is asking for trouble should the two surfaces not match initially and is a bitter experience.
Richard