I think there may be some confusion with the Bondo name being thrown around. The stuff that I like is exactly what Rayp22 pictured in his post. Straight from the tube, no mixing involved, 15-25 mins to dry, and sands like a dream with sandpapers around the 300+ range.
Its not the from a can Bondo that you mix with the hardener tube. I honestly would never recommend that for anything other than filling large voids quickly and yes it is a bee-hotch to sand smooth. Must start with 60-100+ range sandpapers for that.
Also as a side note every single can of mix Bondo I have ever bought has been dented, which I find a little ironic:lol