Yeah, I screwed up but will this work?

I got in a hurry, I got lazy, I got stupid (maybe already was) but I was using my sander and my grinder to remove rust and then paint from the engine compartment. I probably didn't need to take it to bare metal but once I got going, it looked so good. And then the firewall. I got careless, and prepare to scream, used grit number 80. Yep. Left all kinds of grind marks in that nice shiny steel. So what I'm wondering is this, could I go over it say with 200 grit and then, incrementally, work my way up to say 1500 grit and eventually work those nasty marks and gouges out? The inner fender where the battery sits is pitted but not rusted out. I got too aggressive there as well and may try to hit that with a dremel. For those wondering, who cares, it's in the engine compartment (the worst is the transmission tunnel (auto) where the engine would probably hide the marks once primered and painted. I want to learn to do it right. Its that simple. Thanks for any advice, rebuke, and scorn I need to fix this.