I think I used nutes+calmag before. You go til it wastes in any size pot you're starting in right? Then leave it for 24 hrs before you plant seeds for germ?
A lot of the better quality coco is already buffered. If you want to know the correct way to pre-charge - go to www.cocoforcannabis.com.
when i plant seeds i put microbes / compost tea with a little bit of protekt (super weak ppm) clones i just put microbes / compost tea i use canna coco and i just wet the coco and flush em a bit then wet em with the microbe solution. works every time char coir and cloud coir rock too