Ditto on "all the above". If you're doing the firewall, the door jambs, and all the peripheral bits and pieces, you're going to use up quite a bit of paint. Also be sure to use the proper reducer. It's going to be temperature-sensitive, so unless you're doing all the painting at once, you might need to use more than one type of reducer. Just a few degrees of temperature change can have a big influence on the type of reducer you'll need.
Jerry
