I am just a hobby pourer, so this is just how I do things, not necessarily the only or best way.
I shoot some PAM cooking spray into my injector after each shot. That has kept the O rings in good shape for more than 5 years. Knock on wood.
I shoot med fast, and hold pressure for a 5 to 10 count, depending on how thick the bait is.
Good venting lets me shoot faster, since there is no trapped air to get rid of, but each mold is different, so I vary how fast I shoot accordingly.