Well, I had a spare minute today, so I figured I would share my attempt at cleaning up my headers.
(Polishing disclaimer) Before I get flamed, I agree with the ride more than you polish mantra....but, I also believe in keeping my tools / toys at least moderately clean...and having a little pride of ownership is not wrong (IMHO).
My headers are exposed to everything, and especially anything that the front tire rolls through / slings up. After 15K miles...they have a fairly nasty brownish / black crud of road grime and tar baked onto them.
A buddy had told me to grab some of this stuff from Home Depot. I think it was like $5.
I put just about a half inch of water in my bucket, and almost all the can of BKF, making it into a slurry (just short of being a paste)
I soaked my 3M Scotchbrite pad in it, and went to work....
After just a little scrubbing, something was starting to show...
After about 5 minutes of scrubbing....I had a nice dull stainless appearance!
It only took about 35-40 minutes, and one worn out scotchbrite pad, and I had cleaned 98% of the gunk off!
It gave the headers a nice 'bead blasted' look.