Long story short; I'll have the heads and valley cover off, cam out, front cover/pump/chain off, etc. But the engine will still be in the vehicle. I hope to have the oil pan dropped but it won't be removed.

This thing is in rough shape for a number of reasons, not a lost cause, but needs some TLC.

What's the best way to clean what I can while it's torn-down? Can I just use some sort of cleaning agent / degreaser and a brush and let it drain down into the pan and then flush it out somehow? I know I need to be careful not to get trash down between the pistons and cylinder wall.

What's the best kind of cleaner to use?

Can I flush with water if I let it dry?

 

Usually a solvent and a wire brush or the red scotchbrite pads work well for unmachined surfaces, like the area under the timing cover or valley cover. Spray them down with WD40 afterwards to help flush the solvent away and keep parts from rusting. If you're cleaning the deck, just a scraper and WD40 should do the trick.