One of the challenges in polishing is to not do to edges what he did to the frame cutout for the cylinder. The top and bottom are uneven and irregular. This is the mark of amateur work. It is shiny but I think he has devalued his gun a good bit.
You should use a good buffer with three types of wheels, felt for flat surfaces, stitched for round surfaces getting heavy polishing, and loose or unstitched for fine polishing on uneven surfaces. Hand work on edges or rounded internal areas should be done with a backing to stay flat and even and avoid lobbing and uneven edges. Detail work with a Dremel tool must be carefully done.