I’d recommend headphones as audio cues are extremely important for this boss. Listen for the exploding monsters, they spawn most times after he does the move where glows red, which can occur mid his-attack.
Prioritize adds, on Apocalypse/Nightmare only 4 spawn at a time. Don’t bother attacking him until they’re all dead (until you’re confident at least). Learn to bait their explosions. They also explode one another if next to each other when one of them blows up.
Gorefists moveset itself is trivial. I recommend moving to the large open area to the right of the entrance to the boss fight. Be wary of the far right corner relative to the entrance as the adds can spawn above you there, so on cue try moving more to the middle-right area (again relative to the entrance). This is not foolproof, you still will need to listen and adjust accordingly.
When he rushes you dragging his sword, just walk around him to the right. You don’t even have to dodge. His horizontal sweep has deceptively long range, so make sure if you’re unfamiliar with its dodge time to keep your distance including through physical obstructions. I’d say this is the main move of his to be careful of; he can also explode the adds when swinging and if it’s in your direction they’ll blow you up.
But I can’t stress this enough: Audio cues. Tell everyone around you to shut up if you have to. The little whirring of the blow up adds is how you know where to look.