Let me give u my humble opinion, go find a good place and then set up everything and put ur camera to bulb mode 'B' and put ur lens to 18mm manual mode to infinity, connect a wired or wireless remote, for wired remote there shd be a latch to hold on and for wireless u need to hold on. When u hear 'boom' (fireworks that just shoot up) latch or hold on and count one thousand .. two thousand .. three thousand and put ur black card to cover the lens completely ( removed len hood, forget about cockster who say len hood be on at all times), wait and if got another fireworks then take away ur black card and repeat procedure and closed back, all this while the latch shd be activated at all times and when u thin ur done then unlatch it and u got ur nice fireworks .. correct me if im wrong but i tried this for all rehearsal and works like bee to honey ..