Cleaning up rust underneath?

I'm going to be dropping my gas tank tomorrow. So I was wandering what I can do about the bit of surface rust underneath? Should I take a wire brush to the rust then spray black rustoleum? I'm going to need to cut and weld new floor pans. As well as fix a badly rotted rocker. Some surface rust on the bottom of the doors.

I'm going to take a few cans of oven cleaner to the motor, tranny, tc unibody and anything else greasy and nasty (axles). Then blast it with a power washer.

let me know how the oven cleaner works for you....i need to clean the underside of my rust buket also....it has all kinds of flaking metal on it and other road grime.

cheapo dollar store oven cleaner works wonders on grease, grit, and grime. It doesn't do squat on rust though. Once it's clean, you'll want to wire wheel the rusty/ flaking stuff and hit it with some rust converter and paint.