The bottom of my MH is mainly graphics/striping, and they did bleed a bit. Didn't really notice it during the Bar Keepers or TSP phase. If they bled then, it rinsed off easily. The color did bleed onto my rag during the first coat of Red Max. I was just careful not to spread it up onto the other parts of the MH; I turned & folded my rag as I went. The first coat of Red Max sealed them all up and bleeding was never a problem after that (used a new rag starting with the second coat)
Regarding Red Max on metal: My cab was very oxidized and dull the same as the rest of the MH. Chalky, no shine, etc. I used the barkeepers (it's very fine so it really doesn't scratch), TSP, and finally the Red Max (same number of coats as the rest of the MH), and my cab looks like it's brand new.
Go back and take a look at my Jamboree early in this thread if you have any doubts about metal.