I’ve built several small boats (2 kayaks, a small tender and a sailing dinghy) using epoxy from Fyne Boat Kits which is both very good value and easy to work with. Otherwise East Coast Fibreglass is a very good supplier.
    My 4p on epoxy or polyester for small stitch & glue boats is always to go for epoxy for the structural work – the filleting and taping. Whether or not you then sheath it or coat it with epoxy (or even polyester)is much more debatable; it add a lot of weight and is only any good until the film is breached – then it hold the water inside the wood ! I would suggest that you forget sheathing/coating with gloop and go for painting – or even varnishing. For a boat that isn’t going to be in the water all the time (so long as you don’t need show quality) exterior quality house paint is fine.
    Amine blush is a byproduct of some epoxy types curing and is often not easily seen. What it does is prevent subsequent layers of paint or varnish from curing properly, so you need to get rid of it. You can get round it by either (a) covering the epoxy with a layer of peel ply (ECF sells it) when it is wet which is then removed after curing, taking the amine blush with it or (b) scrubbing the cured epoxy with a plastic pan scourer pad and a lot of fresh water or (c) sanding down then washing off with fresh water before painting/varnishing.