I definetely wouldnt polish it, it would take forever and look awful. How bad is your frame, is it just dirty or is it corroded or scratched?

The frame spars are anodised, I have always used car wheel cleaning acid on the cast sections on mine but you have to be careful as it can discolour the alloy if you leave it to long. it really cleans all the grime and dirt from the cast areas well and brings it up like new, brillo pads do a good job as well.

Any small scratches or areas of corrosion on the anodised sections can be polished out with wet and dry and "re grained" with scotch brite to blend in with the original finish.