I would use an orbital buffer for random spiral sanding motion and start with 400 then 800 then 1200 for a mirror shine

cheers dude

try using a little buffer and "fishscaling" it looks very cool then u should b able to get clear heatproof paint from ur local paintbarn in an aerosol. i'm probably wrong but i think thats all u need

ive done alot of polishing and was almost going to do the same thing but my cover had more surface rust and pitting in it than i would have liked so im going to paint it,details are coming up shortly in my thread ,
also if your interested ive wrote a short guide on polishing also in the same thread have a read and have a go if your really keen cheers ,the thread is called
datsun 1200 ute restoration and sale,just search

Evilbetty's thread is good!
Check it out

Lots of before and after pics

why not get the cover cleaned up then get it chrome plated and be done with it?