BB22,
We had great luck with a 4.5" angle grinder with a special synthetic sanding pad made by 3M (I'd give you the number but most of our body working tools are in my Dad's garage). You can get them at any hardware store.
Waaaaaay back when we started our truck (before we acquired decent tools), we used the same disk made for an electric drill. That worked well, but the angle grinder achieves much higher RPMs and makes really quick work of the sanding - right down to metal in no time at all. Plus it has much better durability than conventional circular paper disks.
We also used electric orbital sanders (palm type) for working body filler, ending with lots and lots of hand sanding with a rubber block and sandpaper. If you don't need to get to bare metal, a small electric hand sander will really go along way.
I personally don't recommend wire brushes on an electric drill, since the brush bits break off and fly into eyes or fingers nearby. I will use them for fine angle work when necessary, though.
Those are my opinons anyway (for whatever that's worth). If you want part numbers, let me know and I can post them for you by tomorrow evening.
P.S. I just picked up a pneumatic block-style orbital sander for Dad for father's day yesterday (can't wait to borrow it!!).
