What are peoples opinion on the best way to clean the alloy on a gearbox casing. Cheers. (all pictures of before/after welcome)

I took mine to work and steam cleaned it. I then painted on this special acid we have for alloy wheels and rinsed well.

then a coat of primer and a couple of coates of silver and it looks really nice.

Not a type 9 but used GUNK engine degreaser and toothbrush and pressure washer on the outside of my MT75

Came out quite well no pics tho