Paddle finish

Epoxy as a base coat only really serves as a pore filler so that you get a gloss to your varnish faster.

Here's my protocol, worked out on many paddles:

I use an epoxy tip that is set into the end of the paddle. A fiberglass plate secures the whole thing together in the end of the paddle wood. This tip is a fair bit of work but works for me.

I varnish the entire paddle with one sealer coat of varnish. Then sand with 220. The blade receives 2 more coats of varnish, then allowed to dry for several days, then is flat sanded to 400 grit, then two flood coats of varnish.

The shaft and grip receive 2 coats of Tung oil over the varnish. I haven't found anything nicer, yet.
what kind of varnish do you use, is it marine spar ?
I'm similar to above. Two or three coats of marine varnish on blade and then "polish" with very fine paper to give it a satin finish. On shaft and grip I use tung oil. I've never had blisters with any paddle, but I prefer the feel of oiled to varnished wood.

what kind of marine varnish do you use?

Not wishing to answer for the others but...I've become a convert to oiled finishes over varnish for my paddles, too.
So much so that I recently sanded the varnish off a couple of my Kettlewells down to the blade and then oiled the shaft and grip. It is much softer and the paddle more responsive in my hands after a day out in a canoe.

For the wear and tear on the blade I still use a good quality Marine vanish, but for shaft and grip I use Badger oil, a hemp oil blend.

Hope that helps.