When I did my engine, I removed as many parts as I practically could, then blocked up anything I didn't want water getting into with aluminium flashing tape. Sticky stuff, water doesnt get it off. I then went to supercrap and got some VHT engine paint and half a dozen cans of cheap and nasty degreaser and some metho.
To do the engine, I merely scraped as much dirt off as I could with a wire brush, then drenched the engine with a can or two of degreaser. Let it soak for a bit then hit with a high pressure cleaner. That'll get rid of most of the top stuff.
After that, hit with 2 more cans of degreaser and wire brush again, and rags and scourers. Then, get some white rags and wipe the block and painting areas down with the metho. Keep doing this till the rag only discolours minimally.
The metho will evaporate, but go over the lot with a heat gun anyway to finish off any moisture, then mask and paint.
Seems tedious, but the more you prep the better it'll last. When my engine was later rebuilt, the block was hot tanked, but a few places still had paint on them!
