The only thing that I can suggest is this.
I build all of my rifles from pieces, not built parts. A flat top I have(post-ban), standard heavy barrel with brake, after a few thousand rounds was starting to open up it's group. I knew the barrel was still good, but the muzzle and void where full of crap. I tried Q-tips, tooth picks, soaking in CLP, nothing worked.
The thing that saved me was that I had used silver solder to weld the brake. I heated up the brake and spun it off to clean the void and muzzle. The only draw back is you have to chase the threads before you can re-solder. The rifle is back to shooting sub MOA.
As for just putting something on the end to protect the muzzle, Kurt sells fake FS with the front open. On these, it much easier to get to the void and muzzle.
Also, not considering fouling and bullet striking the brake, the real killer of accuracy in regards to brakes are tighten then up too tight.
If your looking for a source for silver solder, check here:
http://www.silversupplies.com/catalog/silver_solder/solder.shtml#paste