Ok im not saying this is the definitive way to run coco, there are peeople who do things very differently to me and they get amazing results but the way i do things is
i feed them once a day up to about week 3 (to make the roots work)then twice a day. When they are in bloom i feed them 4 or 5 times only when lights are on. all automated for me. I always run things in a smaller sack/pot then u may think is advisable, this helps me to facilitate multiple waterings. I never flush until the end, i just try and keep my e.c low throughout. u shouldn't get salt build up in coco, especially with multiple waterings daily.
i only P.h the reservoir that is feeding my plants. i try not to go above 1.4 e.c at max feed. using this method i can get 20+ from an 8 litre sack. However some people who i know use really big sacks and feed once every 2 days and they also get great results, i prefer this method i outlined because I'm getting the correct ph and fresh oxygen to the root zone 4 times a day.
as far as nutes go I'm not sure what u guys have over there but i use the same nutes used to use in dwc. Oh and i add beneficials to the coco and 40% of my medium is perlite or super soil aerator mixed with the coco