The M6 booster/flashider and the one piece booster are difficult to remove without boogering up the finish even with the bearing wrench. especially the M6 all it has is a couple of flats to put a wrench on. There is a "carbon removing tool" in the TM for this purpose, but you have to remove the flashider to use it.
I took a 4 foot long 1/4 in rod and cut 1/4-20 threads on one end, got a 3/4 in wire brush with a 1/4 in shaft cut 1/4-20 threads on the shaft connected them with a coupling nut.
Remove the back plate, bolt, lock frame and barrel/extension, which you have to do anyway to clean the muzzle end of the barrel, place the muzzle on a rag on the floor chuck the rod and brush in a cordless drill spray the inside of the booster with Kroil , or whatever you use stick the brush/rod thru the back of the reciever box and down the barrel casing, and against the booster, turn on the drill and there you go. Wrap a small piece of rag on the brush to finish cleaning.