If you use paper alone and don't want too many layers, you will probably need to use floorboards, ribs, or some sort of stiffening material. Sand the outside while on the mold. Remove it from the mold and work on the inside. Think through the attachment of wood parts and other components relative to painting or varnishing. Gunwales can simply be glued on the hull and the edges of the hull trimmed off with a sharp drawknife or a small saw.
Some people add a few ribs to stiffen the hull and make it look more like a wood canoe.
Mount decks, seats, thwarts, etc. as best you can manage. Waterproofing is essential . Thus a good grade of oil-based varnish or paint is advised. Some people have even used epoxy and also added a layer of glass cloth for greater strength and abrasion resistance.