5. remove engine block drain plugs.
I don't know what that is, just take the rad hose off the tstat housing, or just pull the housing off because you'll need to replace the tstat anyway. It's at the bottom, so whatever is gonna come out will come out.
The flushing part sounds fine.
I fill the engine back up from the top rad hose. That puts coolant directly into the block. Seems to work better that way. That will fill the engine and rad.
Then as it says. start the engine with the cap off and wait till it warms up (you'll know when the tstat is open because the temp will be up to normal, and hopefully be solid), make sure it doesn't overheat!!! Sometimes getting all the bubbles out can be a pain. It's easier if the front of the car is jacked up too. Helps the coolant get into the engine better... I've always used this suggestion and never had an issue.
Heat on max is good. The whole process kinda takes a while, but not a hard job.
Oh, also, get hose clamps if you have the stock wire type ones. They will break taking them off.