I've just done mine with the Frosts £20.00 polishing kit - 3 grades of mop and compound. It took about 3 hours and the end result, whilst not perfect, is very acceptable. I used up less than 50% of the compound so I guess the cost was <£10.00.
And it was rather satisfying changing a rather manky exhaust into a thing of beauty!!!
Cheers
NigelJ