Well, I described a classic method from Haynes books. What combsie66 said is also perfectly alright, as long as you remember to top up after first run. Just don't drive the car until you finished with cooling...
Thinking of it more, there might be a difference between US, Euro and Jap cars in this matter.
I remember the only US vehicle I drove, a Chevy Rally STX. Over there to get to the heating connectors or to the head you would have to dismantle half of the car...
On Euro and Jap cars, all these valves are easily accesible. Well, except mine. I've got a French car, and they've built in such way, that header tank upper level is below the top level of the head
Anyway, good luck
