i dont have a large compressor, so i bought the porter cable electeric sander/polisher, it was arround $125 at lowes, ive sanded my whole car to bare metal with it, it works great, variable speed helps, you get a 5 inch sanding pad and a 6 inch polishing pad, it has alot of power, and ive never have any problems with it.
its also realy easy to change pad sizes, and its adhesive backed for psa type paper
# 3.7 Amp Motor AC only
# Electronic variable speed dial
# 2500-6000 opm.
# Will replace an air DA sander and is very effective for sanding cars, boats, or other sanding projects without the need for a compressor.
# Random, swirl free action
# Spiral / bevel gears
# 100% ball bearings
# Includes 6" polishing pad and a 6" DA pad