I usually wax the ferrule first then some scotch tape before cutting off the tip. the wax seems to seal it first so it stays clean. I use triple EEE polishing wax. has a very fine polishing compound in it. I get it at woodturning supply stores. One container will last me a lifetime. I guess you could use a polishing car wax also. I also use the triple EEE after installing to clean it up and shine the side of the tip. I also first use a q tip with some seal coat on the side of the tip then wax. It's simple and works for me, professionals may have a better way but mine works with what I have in the shop.