I don't care what the can says, I've never succeeded at recoats that fast.  Epifanes RapidCoat will do that, but not Schooner.  I also was laying it on too thick at first, in cool weather, which caused drips and sags that, because they were thicker, took longer to cure.  In the extreme, I've taken a razor blade to clean off soft blobs because they were taking forever to harden,  Then wait a bit more, sand, and recoat with lighter coats.  With Schooner, I've generally gotten a coat a day in the garage.  If you are outside in the heat of summer, you may get faster times, but only if you go lightly per coat.

I actually put an epoxy seal coat on my spars before varnishing and I don't think it has any bad effect on the varnish.  Actually, it was a seal coat, sand, recoat, finish sand, varnish.  It does reduce the number of varnish coats

On the spars, assuming you have a lug rig, yes, the boom and yard will rub.  I wound up using the same leather as used on oars and taught myself how to use baseball stiches to lace the leather to the mast at the boom and the yard as chafe protection.  Look for how-to videos on leathering oars and adapt.  Looks salty, too.  I had to practice a bit to get the dimensions and tension right to conform around the square section mast.  It helps to have generous radii on the corners.

   Hi Will, I used Schooner for my Jimmy Skiff. I noticed that unless you put on a very uniform, thin coat, it will be soft for quite a while, even if the temperature is warm. I also noticed that if I attempted to clean the surface  (within a few days of application) with lacquer thinner it would eat into the varnish and wipe it away!  But months later, you can rub it with a lacquer thinner soaked rag and it is impervious.  

I guess I'd say wait longer, and do 'sag patrol' for an hour or so after application. 'Sag patrol' is the art of lurking around your boat after varnishing looking for sags, drips, or any other un-holy behavior by the varnish.  You can smooth the touch up and boo-boos for quite a long time before the varnish sets up.  Schooner self-levels very well, so even if you see brush marks after doing a touch-up it will likely 'flatten-out' by the time it dries.

Bottom line is, that stuff must take a dang long time to really harden.

   I've had good results when applying multiple coats of Schooner Varnish "hot" -- I.e., multiple coats in a single day. I wait until it is dry to the touch but not much longer and apply very thin coats to avoid drips. The trick is to avoid getting "holidays." Eternal vigilance!

That said, my varnish coats can take weeks to harden fully. The boats can be used during this period but are easily scratched until hardening is complete. 

As to curing time of epoxy, the longer the better. I tried to wait 4 or 5 days in warm weather. You want it as hard as possible so that sanding just removes the rough spots gradually.

   Thanks guys. I think I made a few mistakes in overcoating too soon and coating too thick, and maybe I didn't mix the can properly (gave it 30 seconds of shake, but probably didn't mix up all the agents). Good lessons going onto the hull and other surfaces.

I think I'm just resigned to refinishing the spars this winter, but won't let it keep me from splashing in the next few weeks.

   Thanks guys. I think I made a few mistakes in overcoating too soon and coating too thick, and maybe I didn't mix the can properly (gave it 30 seconds of shake, but probably didn't mix up all the agents). Good lessons going onto the hull and other surfaces.

I think I'm just resigned to refinishing the spars this winter, but won't let it keep me from splashing in the next few weeks.

    I used Minwax Helmsman Spar Urethane on my kayak and had the opposite problem, it dried so damn fast that it was hard to keep a wet edge and get a good flawless finish. On the positive side I was able to apply 4 coats a day (alternating hull then deck about every 4 hours) so it didn't take too long to get 5 coats over the entire boat.

I worked in my basement and had a consistent low humity temperature of about 70deg. I also let it sit about 3 weeks after finishing before putting it in the water.

BTW - I always heard that you shouldn't shake the can as it fills the varnish with tiny bubbles. I've never tested this, I stick to stirring so it may just be an old wives tale. 

   What Snowbound said is true.  No need to shake or mix, and it will add air bubbles that could take some time to get out of the film.  Pour some into a working cup and go to work.  Seal the can ASAP and use the StopLoss bags sold here if you're keeping it for a while.