Contact paper is your friend in this situation.
Lay it onto the surface of your drumb, Do the kinkos thing, trace the image onto the contact paper, remove the areas you don't want with a razor, press the edges back down if anything lifts off the smoker. From here you can spray paint or use a hand brush to get your desired results.http://youtu.be/xLBy-NNfYfU
This isn't on as large a scale as your smoker, but the concept remains the same. You can get a huge roll of contact paper for a really nice price as well.