Several folks including Armalite say to run synthetic motor oil on the bolt and run it wet. I've done that with mine and have had no problems.
We run Mobile 1 on most of our business' demo guns, many of which are full-auto AR's and AK's. It flat out works, and is dirt cheap compared to anything else out there. There are a lot of great lubricants and cleaners on the automotive aisle, that's for sure!