Good topic. This subject comes around every now and then and I forget that not everyone knows how to do this.
As for the jute twine, that's what I use to wrap my sinew. I've been doing it that way for about 4 years now. I guess I was one of the first to use this method. Got some funny looks when I first started.
Most guys use ACE bandages to wrap the sinew. The bandages breathe and they don't stick to the sinew too bad. I wouldn't use any type of plastic or rubber over the sinew. The sinew needs air... preferably dry air that is moving (like a from a fan).
If the sinew is showing cracks as it dries, I think you are using too much glue. JMO. You don't really need much glue to get the sinew to stick.
The best way to fix the cracks at this point is to wrap the sinew with an ACE bandage and heat the sinew gently. Remove the bandages and see if it helps. And/Or you can brush on thin coats of glue and build up layers until the cracks are gone. You can sand lightly between layers of glue.