The potential problem with Dremels and similar tools is that the polishing action is usually "against the grain" or side to side, perpendicular to the cartridge's travel. I hand-polish using a bit of fine emory cloth followed by crocus cloth, polishing the feed ramp in the direction of the cartridge's travel.

The trick is not to take too much off. I might add that I have several guns, including my S&W M&P, that have never been polished and don't seem to need it.

I might add that since the advent of hollow point pistol ammo, starting in the 60s, gun manufacturers have since learned how to finish their feed ramps while ammo manufacturers no longer use hollow point designs with exposed lead, which, really dragged on rough feed ramps. So, if it ain't broke, don't fix it.