: In a word, you don't. Since you are rubbing it almost dry, I would expect it
: to be a pretty thin coat. You are going to put several on, right? Of
: course, you don't sand between coats, unless you let it dry completely,
: and then very gently.

: NB, I have not done this on boats yet, just smaller projects, like banjos,
: desktop machines, and small projects. I would expect the technique to work
: just fine on my kayak, if I ever get the darn thing finished!!

There is a minimum film build that is required to get UV protection from any coating. I would suggest that you go down to your local industrial coatings supplier and buy a "mil guage" to test this film thickness in your technique. These guages are very cheap (couple of dollars for the metal ones and usually free for the plastic ones.) and then there is no guessing about the durability of your finish.

A banjo would not need nearly the UV protect that your kayak will require. So assuming this technique will work on your kayak may be setting you up for a lot of extra work in the future.

Ian