You can take the coolant drain plugs out, most likely have to jam a screwdriver up the holes to get it to start flowing out.
You can hook up garden hose to heater hose nipple. Or if you feel like taking the water pump off stuff it in the front of the block.
The more junk you can flush out the better. Don't forget to flush out the heater core and check that for leaks.
The valley pan gasket is called the pushrod cover gasket in the book that most local parts stores use.