Flushing a Slant 6

So this weekend, my neighbor and me lowered the slant 6 I am reworking on the engine stand so it is not so top heavy.

Then we rotated the motor so i can get a peek at the crankshaft and the crank bearings and have a look at the cylinder walls. All check out looking in good shape. The oil pan was dented pretty bad and my concern was that the oil pickup was going to be in need of replacement due to being bent. It wasn't effected at all.
My question to anyone out there is this: How do you flush a motor now that i have it on a stand so I can get rid of all that grimey old oil? The oil that came out of the motor doesn't look like it had a lot of water or sediment in it. But I know a good flushing can't do harm to it.