When we put up fence panels similar to that on the south fence in back, we used a garden sprayer to put a Behr product on. I don't think we put anything under it, like Thompson's, but may have put it on after. The fence looks acceptable some 10 years later.
We stood the panels up on a tarp and just let the excess run off onto the tarp. Gave it a pretty good soaking too.
The termites have found a way in now but it's still standing.
Here's a picture of it.
The gate on the right was done the same way.