You want to apply exactly 1% kosher salt based on the weight of the finished curds. For example, if you end up with 400 grams of cheese curds, then season with 4 grams of salt.
Besides the time involved, the hardest thing is keeping everything at those relatively low temps. A sous vide set-up would be prefect for this, but a double-boiler does work. Just keep a thermometer in place, and once the milk gets up to 90 degrees F, alternate between low heat and no heat to get where you need to be.