I've used
Promix for 30+ years and have always had good results with it. I add about 20% compost/manure and a few tablespoons of wood ashes.
Promix drains pretty well on it's own and I never had a need to add perlite.
Promix doesn't have much in the way of nutrients in it other than a small amount to get seedlings a boost, so you will need to feed it after a few weeks in most cases. I mix the manure/compost and wood ashes in to help provide the micro and macro nutrients that plants need, and the ashes help buffer the
Promix along with the buffering that is already in it. Be careful to not overdose on the added lime/Ph up stuff as it often taks a month or two to work it's magic and it is way too easy to throw your Ph out of whack. In my experience with
Promix, I have never had to adjust my Ph one way or the other as it seems to stay between 6.5 and 7 in my setup.
I feed every 10-15 days using a regular 20-20-20 Jack's general purpose and water every day or every other day after they get about 1.5 ft tall... or as needed.
Promix is not easy to overwater as it drains well, so you don't need to worry as much about drowning your roots as long as you have somewhere for the drain water to go instead of pooed around the roots. This is how I do it, but there are many ways to do it that feed constantly or water 5x a day. Pay attention to your plants and just spend time around them and you will soon get to know if something is wrong just by looking at them. Keep up the good work... good luck!!