Was at the store today and picked up a 20# bag of Cowboy charcoal for $9.00 and though what the heck I'd give it a try. I filled the firebox up and got her cranked to 550 for some pizza. 1st pizza was great then tossed and dressed the other one put it on and looked at my dome temp it was at 300 opened everything up and seem to stay, so I lifted the lid and looked down and seen the fire box grate. All the lump was gone in a short period of time. Unreal. I would say the whole firebox lump was gone in 30 to 45 mins, anyway had to finish the 2nd pizza in that metal box that heats up in the kitchen.