Lol toothbrush and petrol...your doing it the hard way man..
Soak bay in good degrease, not cheap useless shit, (ct14 is ace) hose off..repeat process still clean.. There may be a few little spots left that require a rag or brush but not much...
As for painting, by far the cheapest easiest way is to do it with spray cans in your shed..
I did most parts in my bay with heat proof paint and it looks tops. Everybody told me it would peel and flake, 2 track days and its fine..lots of thin coats is the secret..then let it bake slowly on a warm engine for a few hundred kms before getting it too hot.. Awesome result for less than 50$