Paul,
Yes you can but....
Your literally 3 days from being done. You can be in the water by Saterday morning if ya start now. Besides summer is the best season for varnishing. You can take the fumes outdoors. Good drying temp etc.

The trick is to varnish the whole boat rather then half the boat at a time. 3 days verses 6 for 3 coats. That ought hold ya till later.

First you'll have to build a lifting system to raise your yak up. A tree limb a swing set etc. with a rope over it to a piece of 2 by 2 board that fits under your deck and fits through the cockpit. Lift it up and you have access to the whole boat. If you have a sprayer your done. 10% penatrol a to thin the mix go over the boat and your done. Let her dry in the swing for 24 hours.

If your not spraying put soft yokes under the lifting system. Put the boat face down in your yoke. Varnish the hull between the yokes, but leave the ends dry. Walk away and let it flatten out for about 20 minutes. Then spin the yak in the yokes. Do the cockpit and let that sit for 20 minutes. Install your rope system on the boat and raise her up. Varnish the hull ends bow and stern. Then do the deck one end to the other.

Between coats you wait 24 hours. When you get back sand her down. and give her a second coat and then a third one etc.
It takes about an hour to sand her down 20 minutes to wash her down with alcohol and let it dry. And about 30 minutes to put a coat on the boat. and about 40 minutes of waitng time One coat per day

You can have 3 coats gleaming in the sun by Saturday morning!

!RUSS