If you sand it, use a da sander something like a National Detroit DAQ. If your da has a finishing orbit(3/32) it will take forever.
For cleaning out the rust pits you could get one of these, they work awesome.
MBX bristle blaster, other tool companies make one as well. Snap on, mac, matco, dent fix, dynabrade, etc.
http://www.mbxit.com/products/bristle-blaster-c-6.html