Quote Originally Posted by Canuck of NI View Post
I can contribute a very small bit of information: in traditional Canada, boiled wool mittens were created by hand-knitting very large ones from natural (therefore naturally oily) wool and then literally boiling them until they shrank and tightened up so as to be almost entirely waterproof, or if they did get wet through you still couldn't feel it. I had an aunt that was skilled in the process. I believe this concept was an old Celtic fishermans' traditional survival item in the days when their hands would be in the freezing North Sea all day. So perhaps you could buy an oversized wool vest and experiment?
I make gloves this same way. The process is felting. The fabric site linked to in the OP lists fabric which has already been boiled (some people call it fulled).
I don't think the buttonholes would need any extra strengthening, unless a lot of stress would be put on them. I'm interested to see how this project turns out.