It's been years since I've used this coating. I just read the info on the store page, it doesn't say you can and it doesn's say you cannot layer it. So I would have to check to see what's what.
The last time I used it was also the first time I used it and I only applied one coat and I did a really good job of applying just one coat - my normal practice.
I have done one coat on soft paint and it was going really strong heading into the end of year 2 (before it was traded in). I didn't see the need for a second layer. That said, it is resin based and I don't believe a second layer would have hurt at all. The package on my shelf started to dry up around the end of year 2. In hindsight, I would have added a second layer rather than watch the remaining product go south on my shelf.
Personally I would wait 12-24 hours before applying a second coat. In short, based on my limited experience 1 is good, 2 would be better and hardly hurt due to the fact that it is a resin-based coating.
Mike, I'm open to learning from the makers of course.