Maybe this is an old idea, but I never saw it anywhere, so I had to think it up myself. Maybe it will save some time in the woods for somebody.
I have a couple of backup strings all set to use in case the string on the bow fails. To speed up being ready to shoot, I put the strings on the bow at home and stretch them out, twist them to the right brace height,etc., then when I take them off, I keep the end loops in the same plane as on the bow, and tie them together with a piece of string and store them in a ziplock. If I need to use one, I untie the string and keep the same twist in the string as I put it on the bow.
To check brace height, I first check it at home with the bow square, then I mark my arrows with a sharpie marker at the belly face. Later, if I think a string has stretched, I just put an arrow on the string and look at the mark. If it is not right at the belly side of the bow, I can twist the string and set it right immediately.
This way, if I break a string out in the woods, I can put the backup on and be back in business in just a minute or so, and don't have to carry around any extra tools.