Good choice, the glass beads, but they will eat through cardboard, or plastic, and then pieces of your cabinet will fall into the media and clog-up the gun when you recycle the beads. Consider building a wooden cabinet lined with sheet metal. A portion of your glass beads will turn to dust from impact so you'll probably need more than the 5 pounds. You'll need a window in your cabinet to see what you are doing and evening length rubber gloves to protect your hands and arms. Through your window, you won't see much, other than flying dust, unless you hook a small shop vacuum to the cabinet to pull out that dust. You'll also need a filtered inlet to allow air in for the vacuum.