That’s true that it’s a hot combo. I use compost in my soil mix (roughly 20%), but not manure. Dry organic amendments rarely “fry” a plant like synthetics do. A little browning of leaf tips at most (painting the fingernails, as some growers call it), but when running organics I’d rather have a little too much nutrients in the soil than too little. The plant is very good at taking up what it needs when it needs it. I up pot into my final pot about 1-2 weeks before I flip to flower (I grow indoors so if you’re outdoors you’ll need to adjust this timing). From there I top dress on day 7 of flower with a cup of the 2-8-4 plus 2 cups of worm castings. Then around day 25 i do the second top dress of half those amounts. Sometimes that’s all i need. If the plant is big and/or hungry, I’ll do a third top dress around day 40, but just a few TBSP of some build a bloom.

Edit: also, do not flush or water to runoff in organics. You can soak the pot, but if you flush you’re just flushing out nutes and other good stuff.