Everyone needs to find their own way doing these things. I've pressed them in before and had the lot seize up solid because the pin broached it's way in and grabbed on the bush. If you do it by hand you can check it as you go, the trick of chamfering the edge of the pin seems to help very much, as a new rocker and pin can be a very tight fit when assembling.You really only need to support the rocker not the bush, and because the rocker sits either side of the bush you can support the rocker quite easily.