Paint the whole canoe.
First coat, you can only do about 1 ft square per brush full. Work your way around the whole canoe, brush it out as smooth as possible. Apply the second coat right away, and go around the whole canoe. Put it on as efficiently as possible, brush it out as smooth as possible.
Let it sit till it dries out a bit, the wetness should be passed. Then take your gloved hand and rub it it. Rubber or latex gloves work great. You don't really need canvas mitts. If you rub it out too soon, then the filler is too mushy and impossible to rub smooth.
Two coats should be enough.