Brick Trolls are tough to engage in pure melee, particularly for the beginner. They’re fast and hit for huge damage. The good news is that they telegraph their attacks from a mile away and are very susceptible gun parry.
Gun parry typically involves shooting your opponent during the last part of their attack animation—after they’ve closed in, just as their weapon begins its final approach. They will drop to their knees and you’ll hear a distinctive noise. Walk up to them and press R1 to initiate a Visceral Attack.
If you stagger an enemy, but whiff on the Visceral Attack, it’s most likely because you weren’t close enough. It could also be because you took too long, but in general, you should have ample time. Even if you get knocked back, you should still be able to roll forward and get the Visceral Attack in.