You can use the crush jaw rivet tools, or use the good stuff from AK builder (which is what I use). But unless you are building several of them it is not worth the cost outlay. You may try over at akforums.net and see of anyone has a set of jaws you can use.
As for finishing it, if I am doing black oxide I degrease it, use stripper on it and then wash it with brake cleaner. If I am doing a spray finish I blast it with fine media grit, then repeat the above process. I have also found that if you heat the gun up to hot to the touch then spray it, and let it cure for a week or so before you assemble it.