What is your goal? Do you just want to clean up a piece to use it? Or are you looking to make it into a mirror?
I gave my brother and his wife a Magnalite roaster as a wedding gift. It was a lot of work, but I made that baby shine. To start, some of the bigger spots that were a little ugly were wet sanded with 600 and 1000 grit paper using WD40 as the lubricant. Next came the 0000 steel wool, also using WD40. Then came an hour or two with the buffing wheel. The last step was hand buffing with Simichrome polish and a tee shirt.
My recollection is that for the inside I used either steel wool or a Scotch-brite pad and scrubbed it out. No polishing on the inside.
