Mark,
You must put it on a lot thicker then I.
When I was varnishing my strippers or painting a W/C, I would figure/use just over 1/3 qt per single side, ie, just 1 coat on the outside (or inside).
For 5 coats of paint I would use just a little less then 2 qts total.
This also assumes little loss, ie, you'll use more if you use a roller.
For this project, I (FWIW) would order 3 qts. Or maybe 1 gallon if I had some spare cans to repackage it into.
You don't want to work out of the container, either a qt or gallon, poor it into a small cup or other container and keep the main container closed or the solvents will evaporate and the varnish will start getting thicker.
This gets more important as you get closer to the final coat, the early coats don't matter as much, but after 4-5 coats, you will be looking for it to be done.
Dan