My 1st step is and has been to get a
loose fitting patch wet with Hoppe's #9 and pass it through the bore, starting at the chamber end. This can be done with any gun I have ever owned, bolt or otherwise. Let it set in there for a few minutes, then mount a brass brush at the chamber end an pull it through. Stick a piece of cloth in the chamber to protect the boltface and cover the feed mechanism in your lever or pump or auto action, then run the brush through the bore for 6 passes (three each way). It ain't going to hurt the brush. Then run loose patches through, one pass each way (think about that, what surface of the patch touches the bore each pass), changing patches until they come out clean. Then look at the well-lighted bore and see what is left in there. A little copper shine is probably a good thing. A little lint from the patch may mean you need a different bunch of patches, but one more pass may remove it.
Damn it, this ain't rocket science. Sorry about getting cranky about this, Buster, it's just that some folks are too blasted 'scientific' about stuff.