Sand paper is usually not a good idea. The grit gets imbedded into the bearing. You can carefully scrape the high spots. The issue with cam bearings is you knock out the old and install new ones with surgical precision. Not a knick, not a scratch!!! Then you go and try and install the cam and it won’t turn!!!! If you get it in!! You can send the block out to have the cam bores “corrected” if you can find someone who can do it correctly or you can do what I did and cut diagonal grooves in an old cam core, lube it up and slowly turn it as you push it in. Pull it out frequently to clean out the grooves and relube it. You can cry a bit at this point, I did, once you get it in and turning smoothly. You need to clean the oil galleys. It’s heart breaking, but works.