I have the same SureFire muzzle brake and suppressor (FA556K) on my SLR15 that Rich has on his Grail. The brake (MB556) is very efficient and is one of the few brakes I've seen that will not render anyone close to it combat ineffective. It does not work worth a darn as a flash hider, in fact one might call it a flash enhancement device.
SureFire does have a flash hider/adapter that works with their suppressors. The part number is FH556. I have not tried it personally, but from outward appearance it looks like it should work as well as the standard "birdcage" FH.