What's a good way to initially tighten push rods after rebuilt?

In my opinion, setting valves "running" is silly. So you can use this same procedure, hot or cold

When cold, add about .002" to the hot lash specs

In order to be sure you have the valve you are adjusting on the "backside" of the cam, do this

EOIC

Which means

When the EXHAUST starts to OPEN, you adjust the intake for that cylinder

When the INTAKE has opened and is nearly CLOSED, adjust the exhaust for that cylinder

This method works on any engine from a Briggs to a Merlin

I couldn't agree more. It's actually kinda dangerous. You can end up with a wrench in the eye. Not a good day. I never recommend adjusting while running, I don't care what anybody or any repair manual says. It's stupid.