Ben, I have been moving away from the pothead gurus myself. Moving away from cannabis specific brands as well. Seems the industry is full of predators taking advantage of new and ignorant hobbyists.
I never tried the osmocote, but I am open to experimenting.
The slow release feed seems ideal for long growing sativas.
Any thoughts on mixing it throughout the medium vs scraping it into the top few inches of soil? Does it need any additional calcium? Maybe lime added to the soil as well?