Experiment with the sound of sweeping on the floor. Pull and push the broom and listen to the difference in sounds. Try short and long sweeping motions; with the latter, walk along with the sweeping and time your footsteps as a rhythmic part of the music.
Tip the head of the broom over, tilt and knock it back and forth for a dry, clicking sound. Lift and drop the entire head of the broom for a louder dry hit.
Hold the broom by its head and knock the handle on the ground or on nearby, hard objects. Take advantage of the maneuverability of the handle to rattle it between items such as metal bars or lattices, creating fast hits and taps.
Test the barrels with a variety of types of sticks. Try traditional drumsticks for dry, quick rapping, short metal poles for a loud, ringing sound, or bass drum beaters if you're working with metal barrels or barrels made of other thin materials and want a booming sound.
Try out the sounds of the barrels when they're right side up vs. when they're upside-down. Beat on the bottoms when they are overturned. Test these different arrangements with multiple sticks.
Strike different areas on the barrels and strike at different angles. Strike the sides, bottom (when overturned) and insides (when right side up). Strike the metal bands and the wood on wooden barrels. Strike the top or bottom angles with sticks. With small barrels, rattle sticks inside the mouth, striking both sides rapidly.
Combine the different sounds you've discovered to improvise percussion beats. Choose six or seven of the sounds to create a separate palette for each new song/session. Keep to the same sticks for each session, but switch them up if you do multiple sessions or play with multiple players. Use a combination of dry, rattle-like sounds and booming, echoing sounds in each set. Go for variety.