Probably should have taken pictures
No, I have converted over 4 WTB rims at this point and didn't fill any of them. The first couple I used a very narrow strip of Gorilla tape down in the ctr channel. What I don't like about that approach is that there is very little tape at the edge of the spoke holes. They have held up fine though.
This time around I used about a 1in wide strip. I pulled it taught and worked it into the ctr channel all the way around, making sure it was tight and bubble free to the rim bed as well as the channel walls. Then I carefully laid the excess tape down in the bead seat. I mounted the tire with tube for 24hr to really set the tape. I did prep the rim first FWIW (sanding and scotch brite with attention to the joint region). Standard operating procedure from there on though. Throw a used valve stem in, some stans, partially seated the tire by hand, and aired it up by compressor. I did have to add a bit more stans and coat one bead with stans as the beads were leaking a bit initially (I mounted the tire dry, so not really a surprise there). I did plenty of shaking and flipping, but after the initial couple of minutes there was no more leaking. It has been holding pressure fine over the last week and a half. Still waiting on my frame though, so it has no ride time. I am not too worried, usually the initial sealing is where things are the most issue on tubeless.