Good morning!
I went to tubeless a while back. Using the full Bontrager kit on some Duster Elites. Bontrager sells a hard plastic rim liner and a valve stem that fits into a recess in the liner. I don't know if it's a poor design or operator error, but the valve stem was never secure in the recess. I could poke the stem with a finger and hear air hissing out. The stem would twist out of the recess with very little torque applied, such as removing the core.

Gave up and went back to tubed.

Recently I went back to t/l with one wheel, but using DT Swiss 25mm tape (rims are 22mm), Muc-off valve stems, and FSA offset rim washers. The Muc-offs seem like a nice product. I used the rectangular "foot" because it settled right into the rim's center channel and seemed to provide the most sealing surface around the hole.

I have a slow leak or leaks. Losing half the air after a day or two. Yesterday I started rotating the rim several times a day, hoping sealant finds leak(s). Haven't taken a ride yet.

Does anyone have any suggestions? Seems to me that dipping the wheel into a water tank won't tell me much unless it's leaking right at the valve stem, or along the bead. Bubbling at the spokes would be meaningless because the air could be coming from any spot on the rim tape, correct?

I also thought about adding a double dose of sealant. I put about 35cc in the first time.