I took a half round diamond coated needle file to a new stainless Colt Combat Commander .45 last year. That damned thing had razor sharp edges!
Use electrical tape to protect the flats from slips and just break the sharp edge, don't work it down to far. I ran a fine line at a 45 degree angle around the slide and dust cover with magnifying goggles on then "hand-buffed" the edges with a grey Scotch brite pad. Worked great.
If you've got five thumbs, I believe Cylinder & Slide works on PPKs and can make them feel like "a worn bar of soap" to your hands... but that takes alot of work and will cost you appropriately...