I've used both ways, if you can use a breaker bar and socket on your motor in the car then I would use the set them at top dead center on the firing stroke method as long as you know exactly were TDC is on each cylinder such as having a crank dampener with 90 degree markings so you can turn the crank to each one of them in the firing order. I'll pull the distributor cap off so I can either start at #1 or # 6 cylinders and go from their so I only have to turn the motor over two complete crank revolutions to set all eight cylinders.
If your going to use the ex. valve opening method to set the intake valves and the intake valve closing to set the exhaust valves be careful on bumping it over on the starter a little bit to much
Pulling all 8 spark plugs out using a breaker bar works well for me