Basically I always flat sanded the knife on a sheet of 100 grit paper by hand, vigorously moving the knife back and forth. Takes some time... then I round the edges with a file and back to the paper. Work up through the grits till I get to 600. When the knife has been thinned down to where I like it, I weep some thin CA glue into the pins ( with the heads sanded off there is nothing to hold them in place now), and the edges of the scales, making sure to keep a paper towel handy to sop up any excess, mind those fingers!, that thin CA can set up real quick and glue the paper to your fingertips or even burn you as it sets. I use a combination of sanding blocks and dowels wrapped with the different grades of paper to finish the metal up to each level, being mindful to keep the radiuses even and pleasing to the hand, it's a labor of love.
When the knife has been thinned down, the tricky part is next. Knocking out the pivot pin and re-pinning the blade to make the knife stable and secure. By sanding, you have removed the swell of the pins where they meet the surface of the bolsters, so any lateral force applied will let the bolsters splay outwards and give you side to side blade play and a depression where the pin is.
Use a 1/8" pin punch and drive out the pivot pin. Cut a piece of brass 1/8" pin stock a little longer than needed, like, 1/8" or so excess each side of the bolsters. You can just sand a bevel on the 1/8" brass rod and insert it through the bolsters/blade/bushing assembly and scratch your cut mark on it, then chop it off with a cutting wheel and a dremel. Now you need a flat hard piece of steel to lay the pin on( while it is assembled) and a hammer to peen the pin to swell it a bit making a tight mechanical bond to the bolsters. A light hammer is all that is required, I prefer a 4 ounce hammer for this. Lots of taps going around the pin. A single edge razor blade can be used as a shim to prevent over tightening the joint, but I have always just free handed this step. Once the pin has been peened you are on the home stretch, file the pin flush to the bolsters and re-sand the bolsters and the rest of the knife. Final buffing can be done with a felt wheel on a bench grinder with metal compound.
A belt sander or bench disc sander will save hours of time and labor, Labor for me is cheap

Feeling of having a one off custom self modified Buck knife...Priceless :thumbup: Good luck Bad.