The Fox Farm Grow Big is for veg. 1 teaspoon per gallon is about right depending on how big your plant is. I'd start at 1/4 or 1/8 strength and work my way up unless your plants are pretty big - I'd still start a little less until I see how the plants react, it's better to do too little than too much.
You want Tiger Bloom and Big Bloom for flowering. Fox farm has a feeding schedule on their site with the amounts.