Actually, the best flash suppressor is of the sound suppressor type for those of you who can, have a can. AWC is by far the best, with a 5.56mm can that can be used in CQB/OPS.
Any other suppressor can be identified through 3rd+ gen. nightvision and thermal imaging sights.
As for the standard flash suppressor, "Smith Vortex twisted, and hardened style are the best", they are open ended, by have provisions to pit bailing wire on them to effectively prevent the branches from getting captured in the suppressor!
Pro's often us burlap to shroud that crowned muzzle of precision weapons, which is even better that standard flash suppressors, but it takes plenty of practice for this option, to perfect it!