Bob,
I agree with Zach on the walnut oil. It doesn't smell bad, so your friend could apply it in the shop, then bring the bowl inside to cure. I assume he's already wrapped his shop in 6 mil plastic to keep out the wind.
One other option is to make a drying box. I made one for the fly rods I build and it works very well. The rod dryer is a simple plywood box with holes and poorly fitting doors, but 60 watts of halogen puck lights keeps it at about 80 degrees in my 60 degree basement. (All temperatures in old fashioned Fahrenheit, Prof. Boehme)
My formerly unheated shop would usually be about 20 degrees above the outside temp, here on the west side of the pass. He's got more wind but a little warmer climate, so a couple of 60 watt incandescent bulbs in a 30" cube of plywood should be enough to keep the temp above 65 degrees, warm enough for finishes. A box would also help keep dust particles from getting stuck in the finish, as well. Obtaining incandescent bulbs will be a problem for the future, but as long as the feed stores sell chicks, there will be some sort of warming bulbs available.
