Good to know! I just lost a day due to spraying epoxy over a tiny 1/8" burn-thru because I was afraid of Turbo on bare metal.Small areas we do in dealerships every day.
But larger areas epoxy first.
All 3 of our primers could be called direct to metal, i just dont like the dtm term..
I don't think you can go wrong with any of the three IMO. I've used all three, Turbo, Hi-build and regular, and they all perform nicely. Hi-build really needs a big gun. 2.0 minimum, even bigger works better...