To drain the coolant completely. Well, as completely as possible, you'll need to pull the covers off the bottom of the engine that protect the push rods and remove the 6MM allen wrench sized bolts that are between each cylinder on each side.
I usually pull the lower hose off the radiator as well. In fact, when I do a flush and fill, I usually pull the radiator. Only because I don't want to get soaked laying on my back putting a garden hose in the radiator. I pull most of the hoses I can and flush them with a garden hose. Make sure you open all the heater valves when you do it.
If you don't want to get that involved, I've had good luck with those 10 minute flush bottles you can get at NAPA or CarQuest. Even the prestone stuff at wally world works. Follow the directions and you should have decent results.
Bleeding isn't too hard. Just a little time consuming. Put the front of the bus up a little and open the bleed screw at the top right of the radiator. After about 10 minutes or so or once you get the coolant as full as it can and no more air comes out of the bleeder screw (you will need to close it and open it will bleeding), top off the overflow tank (behind the license plate) as much as possible and take it for a ride. I usually leave off the grill and find a nice hill and park facing up, leave it running and loosen the bleed screw again. Once that is done, the radiator cap should do the rest. So long as the cap is working. There shouldn't be any air in the coolant tank with the radiator cap. Monitor the overflow tank for a couple of days. It will go up and down just make sure it doesn't drop below minimum and you should be good to go. If all goes well, you should be done once you've bled the system out.