IMHO min-wax is a waste of time. It simply does nothing to protect the boat from UV. I tested it side by side with a bit of Marine varnish. ( Epifanes) in an effort to see if I could save money. I placed a strip of wood over the board out in the sun for a week. Major color change in the Min-wax and none in the Epifanes. I just spent about $150 on 3 quarts of Epi for 3 new boats and would not use anything off the hardware store shelf. Marine Quality Varnish!!

Varnish will act differently based on the substrate you apply it to. Wood, cloth, epoxy or whatever. Temps will vary the cure time as well. I have varnished in the shop and waited until the boat was tacky enough to bring into the living room while I am away for the day. The 70 temp in the living room will finish the cure nicely. Colder temps just take longer.
Varnish can be touchy and I would follow the directions carefully to avoid having to start over again not to mention having to remove varnish that is not laying out right or flaking off. Having said that, I have applied several coats in one day, just waiting until the varnish is cured enough to roll on the next coat. That worked great, THIS time.

Robert Visionary.