Karl, the mill has already changed pretty much everything for me, in a good way!
The hemp I use is the kind you get from a craft store. I think they use it for making hemp jewelry. I would normally wrap it 2 layers thick, to make sure there are no gaps. You can also put pieces of leather under it if you want the handle to be thicker.
For sealer you can use epoxy, or what I like to use on my Japanese style knives, is Minwax wood hardener. It is the consistency of water and dries rock hard. I just keep saturating the handle using a small paint brush, until it is soaking wet. It leaves the natural look and feel and you don't get the globby look like you do with epoxy.
I do occasionally use jute twine on more user grade knives. You can Pm or email me if you have any other questions.
I hope this helps.