myself i like to take the finish down to at least 600 and most time i even stone past that to 1200 before i start my cuts .
that way i dont have to worry about blending in un even surfaces .
all thats needed is to then use engraving white or other coloring. then place the design .
IMO you need to at least get you back ground to a consistent surface that will not hold color
this isnt finished yet . still working on back ground removel
this is the side plate on the same rifle
still alittle more work needs to be done , but its coming along