1959 black 270hp (9/2/69) 1981 Beige L81(10/20/80)
At work I use a wire wheel on my much abused big brass hammer when I debur it. Cleans it up and polishes off the grinding marks but doesn't smooth out the metal very well. It can actually erode it in places.
If you want a mirror finish you will have to sand it smooth then start with the courser polishing wheels. Work to the finer ones and then the buffing wheels and coloring compounds. If I remember right, Eastwood sells complete kits for polishing intakes ect.
I realy don't think you will get a job you will be happy with without removing the manifold. Sounds like a winter project to me.