Here is a link to the kit I used when I fire lapped my son's Bobcat. there is a link on the page to the instructions also. http://www.midwayusa.com/eproductpage.exe/showproduct?saleitemid=646612&t=11082005

The abbrasives used in the kit are pretty coarse so be careful and recheck often. I would only use the finest grade if you only need to smooth it out a littlebecause metal is easier to take off than to put back on.

The JB's is good for a final polishing (you could probably even use the fire lapping method with it).

Here is another link to some info on lapping a barrel. Not all of it applies but gives some interesting reading.
http://yarchive.net/gun/barrel/lapping.html