Hi Julian
Hot wash, warm rinse, or warm wash, warm rinse.
It's rare for me to use cold, and if I had to, I don't think I'd use this mix.
Haven't really used the STPP much with this!
I only use STPP on occasion, and on occasion I'll use the Calgon liquid water softener. It's not near as good as STPP (compleatly different) but probably better than nothing. When using either one, I add to the water before hand.