Step 1: Ready, Aim
1) Paintball gun (.68 caliber)
Light a groundbloom and time the fuse length. Ours range from 4-5 seconds, depending on the type of groundbloom.
Step 2: Fire!
Light the fuse and drop it into the barrel. Count to x seconds (where x is the fuse lengh), and fire the gun.
You can wait to fire the gun until the groundbloom ignites, but that may overheat the barrel. You don't need paint, but firing balls along with the groundbloom improves height slightly.