What Jeff said. If you have any scarf joints or the stem/stern pieces that need to be glued, use TBIII - as long as your joint surfaces match well and you clamp well. I have made all of my paddles with TBIII and not only have they never failed, but they also have spent a lot of time in the back of a hot canopy enclosed truck. Use epoxy when you have gaps or situations with less than perfect surfaces.

I use oil based polyurethane or similarly spar varnish for the skin, and you can use it for the edges of the plywood as well. I always tung oil my frames. The basic difference between regular exterior plywood and marine plywood (besides the cost) is that marine is guaranteed to have fewer voids.

There are three ways to join the frames to the stringers. Lash, lash, and lash. With artificial sinew. Don't bother with screws, dowels or glue. And for the skin, I like nylon. Even 7oz. is fine.

Here are my boats: http://paddleandoar.com - My first boat was made with regular exterior ply and pine and lashed. Nylon skin and oil base poly paint. It has been abused by being left outside since it was made. It filled with water and froze. The owner never cleans it. I looks awful, but is as seaworthy as the day it was born.