Vapour blasting.. Not!

[Mr Gazza]

I am trying to clean up a Commando head during a couple of days lull in work.
My favourite would be to vapour blast it, which in my experience is a brilliant way to clean it and leave a lovely smooth peened finish which seems to be very resilient to oil staining and looks nice and bright and fresh.
I don't think I can get it anywhere to blast it right now, so I have had it in the ultra-sound cleaner and also scrubbed it with clutch and brake cleaner. It's now spotless and void of oils and crud, but it's still not bright. It's in the dishwasher at the moment for a cycle to see what that does.
Has anyone got any suggestions as to what I could use to brighten up the cast finish alloy? It's getting between the fins that's the tricky bit.

Thanks in advance.