I tried the white glue and it didn't seem to help. I did change something else. As I continued to spread the blacktop thinly, I noticed the black gel paint seemed to be getting used up. So near the end of the spread, and mixed in a little more gel to get it darker and sticky. It didn't get any stickier but it dried looking good.
Probably somewhere near the end I'll figure out what is going on to get a better mix. In the meantime, I'm happy with the finish. I just have to get better at spreading it when it would rather stay on the blade, then stick to the plywood surface. It seems like if I leave it to rest on the surface, it penetrates somewhat and helps with the spreading. I think the glue actually prevents this from occurring.
