I'm a newbie but I'm using gaia green for autoflowers with promix hp mixed with extra perlite and and 20% worm castings and some dolomite lime. I mixed 2 tablespoons of 4-4-4 per gallon and germinated directly into my final 3 gallon pots so i don't accidentally transplant shock and stunt the autoflowers. At 4 weeks I do 1.5 tbsp per gallon of 50/50 444/284
I'm at 4 weeks now in my 2x4 tent with 4 autoflowers and they are just starting to stretch and i'm about to top dress 50/50 of all purpose and bloom tomorrow. Every two weeks I've been doing a earthworm casting and kelp meal tea steeped in water from my rain barrel for 24-48 hours (more determined by my schedule than any reason to let it steep). 2 of my autoflowers are fast flowering and this is their last feeding for the other 2 xxl strains I will give them another tea in 2 weeks and another feeding in 3ish weeks with 1 tblsp per gallon of 284 bloom.
I sort of mixed and matched this method from mr canuks grow on youtube, and a blog called marijauanamama420
http://www.marijuanamama420.ca/my-nutrient-schedule/ and my own experience using pro mix to grow fruit and veggies in my garden.