Yeah, I am just experimenting as well at this point. The first try of 17% spirits went on without bubbles, but may have been a bit thick. If I can go thinner without creating a lot of bubbles, I will so it can self-level better. But today I know I used too much in spirits. I will try something in the middle tomorrow. I'll post here with those results.
I realize there is no hard-and-fast rule because temps and humidity will vary from one region to the next and one day to the next, but I am trying to get a rule of thumb to get in the ballpark.