Tailpipe and rear box or whole exhaust???

If tailpipe and Rear box then AutoSol fed on with a rag in circular motion till your arm hurts is very good and shines like a mirror.

For the whole exhaust i would hazard a guess at using a fine wet and dry with a machine, followed by Autosol...Hard graft for the whole thing, but a few hours work if just doing the rear less heated part!!!