I also bought the HF unit. I haven't used it on a car yet, but it sure cleaned up some metal I had for a new gate. It looks to be identical to the Eastwood surfacer and is probably manufactured by the same company.
I got 2/3 the car done with pam sander and 40 and 80 grit in couple days. Bout there. The compressor works good for paint but too small to run the DA all the time.
I youtubed the Eastwood model, then got one from a member. It's a major work saver. You can get sanding rolls for many applications. I highly recommend it.