When I had to do my engine, I put a large baking tray (one that had been retired from baking duties!) under the entire engine and a pan of parts washer solvent under the are I was working on. A couple different stiff brushes dipped into the solvent and scrub, starting at the top and working down. The solvent and grunge that ran off was mostly caught in the pan, and and was reused. The rest landed on the tray. Once I was satisfied, I used a can of aerosol brake cleaner to rinse off the residue.
I used parts washer solvent because it doesn't evaporate quickly and it isn't corrosive. It may swell seals if left on for an extended period of time, hence the rinse with brake cleaner.