I did the same for the barrel bushing on a standard-frame 1911 I just built earlier this year. But I used 200, then 300 grit wet-or-dry carbide paper. Using it wet removes particulates as they form, so the paper doesn't gum up. Just smoothed the barrel in the contact area, then fit the bushing I. D. to it using the paper on a hardwood dowel. Same with bushing to slide, smoothed the bushing O. D., then fit the slide muzzle I. D. to the bushing.
I got the Para Ordnance slide very cheaply from Sarco, when they got a lot of Para Ordnance surplus when it was sold to Remington, new guns rebadged, and the old parts bins cleared out.
So now my Colt beaver-tailed frame, Springfield-barrelled, match-triggered, fitted-bushing gun (with spring guide) calls itself "Para 1911 Wild Bunch" on the slide.
I could have fitted the slide to the frame, but had a real fine gunsmith do it, so when handed down to a grandchild, he will know that he has a very special gun, put together by his grandpa, and finally checked out by the best gunsmith (who really liked my trigger job).
I haven't had a chance to shoot it, but I think I'm going to be really pleased with its tight groups. I hope.