vapour blasting is probably too harsch
"caustic soda" for "toilets" ( in gel form not the oven canister one) works well but
1) don't leave the part too long in it - I use a stainless steel deep dish which I place in the sink
2) dont be "scared" by the blackish colour that is produced - it cleans with a brush and liquid dishwasher
3) may need a second run ( shortish)
4) polish - yes corners can be tricky !
5) be careful during the process........