Do the burn out and then take a white wheel to it. Then wash out the drum.
A drum doesnt need to be a food safe drum to be used as a UDS. What makes the drum food grade/safe is the liner which you will be removing. Any drum with a liner needs to have the liner removed, so it doesn't matter if the drum is foodsafe or not when purchased.
*Weber Mini WSM* *Weber Touch and Go Performer X3* *Sublime Smoke UDS* *Maverick ET-732 * World's Fastest Blue Thermapen **Pitmaster IQ110*