Your post was some time back but I thought I would drop a suggestion in the hat anyway.
I have done this on the flats of Colt auto frames. What I did was lay down a piece of window glass. Then put a sheet of new wet/paper down of what ever grit if wanted. Then I added 30w motor oil on top of the paper. I clamped down a piece of plastic stock that I had to use a s a guide so the sanding marks would all be the same direction. I would hold the part, say the slide with the sufrace to be sanded down on the oily paper and I would put duct tape on the top of the front and rear sight. The tops of the sights would then be held up against the plastic straight edge and then the back and forth motion would start.
Hope this helps, I know it is late in the game for advice but what the heck.
Good luck,
~Randy
