A variety of things, it depends how bad it is. I rate autosol - it might not give a mirror finish on ally but I have always found it gives an easily maintainable finish.
Duraglit is not very abrasive at all, more for removing tarnish off gold and silver in my opinion.
I thoroughly recommend you get some kind of mechanical aid, it makes an awful lot of difference. Even if it's just a cheap dremel copy.