Dude...its your freind. Give him something easy to work with that wont burn the shit outa the plants. Am mend the soil supersoil style then just water or add foxfarms organic ....its the big bud I think...durrived from worm castings and guanos. That shit works pretty ok and is pretty damn easy on the plants. Pretty hard to fuck em up by burning them, Give him a bottle and tell him to give them 1 shot glass per gallon of water. plants In a 5 gallon pots tell him to split 1 gallon of water...feed every other watering. Add liquid koolbloom or something more organic around week 2 or 3 as a flower stimulant.
Dont premix yur nutts...hehehehe