small pole barn advice

Definitely use a powered compactor, the thickest vapor barrier you can, line the skirt/grade board with insulating foam board and cut plenty of expansion joints afterwards, along with using whatever rebar/mesh you can. If the concrete truck can back up right to the opening or if you can afford a pump your sure to get a higher psi mix, but if they have to use a buggy or similar I think the crews typically want the mix wetter (which yields a lower psi) to give them more time to work it. A good pour crew is key as I'm sure you're aware.