I guess the lower the temp in the pot, the slower it thickens. its not much trouble to thin a little, but getting it too hot might weaken the glue from what I read.
I get the threads applied and where you want them, and do not worry too much about extra glue or loose ends, even if the glue is gelling too fast.
once the threads and wood are together, you can easily warm the whole assembly till the glue un-gels and apply finger pressure to smooth out the surface and wring off excess glue. hide glue is different, and easy to play with by changing temps.
Practice with string and an old board to develop a technique.