What kind of slag were you hitting, the heavy fused stuff or the lighter scale? That'll tell me if it's a power issue or just junk getting in there.

wait hold on, what was the trick? i gotta know because cold bots are the absolute worst right before a gig

It's just like using a sledgehammer to drive a finishing nail. Bigger isn't always better, it's just heavier and takes longer to set up. People grab the fanciest tool because they think it makes them look more professional, but on a simple run like that 10x12 you just need to take your time and feel the carpet. Overcomplicating small spaces makes more work than it saves.