Sorry for the delay in getting to this. Since that post, we have had 14" of snow, downed trees, Christmas road trip, then 8" of rain and flooding. Oh, and the old engine in the truck started knocking (joy).
Anyway, got to it tonight. The whole process worked out much better than I feared. My goal in all of this is for the drip edge to be weather tight, not looks.
Before the Christmas road trip, I had sprayed on a coat of 2K Epoxy primer that I got in a rattle can from Advance Auto (who knew?). Primarily because the 3M instructions indicate to apply this on a 2K primer or bare metal. This will be the beige color in the pics below.
Along with the 3M 8307 Self Leveling and the 3M 8308 heavy body, I also ordered the 3M gun (3M P/N 8571).
Attachment 1852632
I started with the vertical portions of the drip edge and laid down a pretty thick bead of the 3M 8308, starting right at the top of the upper curve. Then I simply used a gloved finger to smooth it out, trying to press it into the seam without squeezing it out. I left the beginning of the bead pretty thick, so it will act as a dam for the self leveling 8307.
Attachment 1852629
I also had a spot at the upper right corner where there was about a 1/8" gap between the roof skin and the rest of the metal that I filled with a small bead of 8308. Once both sides were done, I let it cure for about an hour, then took the 3M 8307 and got after it. Starting on one side, I began filling the drip edge, and worked my way around to the other side. The 8307 is definitely thinner than the 8308 and leveled out nicely.
Attachment 1852630
I then let that cure for about an hour, then masked off the cab and sprayed a coat of basic white rattle can primer over the newly sealed drip edge. Nothing fancy.
Attachment 1852631