I just finished up my replacement front 10b.
I disassembled it and worked on it in pieces but here's what I did...
Putty knife to scrape off all the engine drippings, sludge, dirt, and peeling paint.
Wire brush the loose rust and dirt off. Big ones for the large open areas and toothbrush sized ones for the corners and such.
Degreased with degreaser/soap and water, hose off and let dry or blow dry with compressed air
Brushed on Rustoleum dk red primer from the quart can.
Let it dry at least a day.
Brushed on Rustolueum semi gloss black from the quart can.
Looks good and so far pretty durable, but I used cheap brushes and I thought I picked out all the brush hairs as I went. But I still find them now stuck in the paint. So, if you go this route, use better brushes.