I honestly do not suggest you use Krylon Archival Varnish… It is not that great.
But I’ll tell you real quick how much time you need to leave between multiple coats of the varnish.
You need to leave whatever you’re spraying alone for at least 24 hours. It needs time to properly cure.
You will want to place it in a non-dusty place away from bugs. Dust absolutely will stick to the surface and become permanently embedded and for god knows what reasons bugs are attracted to the smell of Krylon’s spray. I cannot tell you just how many spiders crawled onto one of my paintings when I sprayed it with the varnish.
Unlike with spray paint, the ingredients of Krylon’s Varnish doesn’t seem to allow you to do another coat on top of one you put on ~ 20 minutes previously OR let you only wait 12 hours.
If you put on another coat of the Krylon Varnish before the previous coat completely cures, the coat will become extremely tacky to the touch and may never go back to normal.
*Read the directions on your can and then add more time to create a margin of error for whatever climate you’re in.