Re: Wait time to apply 2nd layer of glass with Epoxy
tennpenn,
Don't wait for it to completely harden, you will have to rough the surface. There should be some recommendations on the product you are using. Generally, the epoxy as it cures will release gases (this can cause bubbles in the glass), you want to make sure you are not laying up too much or overcoating too thickly as to not allow the gases to escape.
It is also going to depend on the cure rate of the epoxy you are using, slow cure? fast cure? All of it makes a difference in the layup.
If you are unsure, wait for it to set, then lightly sand before next coat to remove the sheen.
Peace.
Ed.