I use Liquid Kool Bloom and Dry Kool Bloom, personally. The LKB is for preflower up until the last 2-3 weeks before harvest. At that point, you stop administering LKB and begin giving Dry Kool Bloom. The LKB has a hormone (and P+K) that helps your plant speed up it's flowering process, and helps to add budmass. The Dry Kool Bloom is for the last final push to harvest, to really help pack on extra weight. If you're still really new to growing, you may choose to avoid bloom boosters until you've done a few grows. Or at least use it gingerly.