I use 40 lbs of briquettes in my pr60, that gives me 14 hrs or so at 250. I think that should work for you at 300, as your cook time would be less. When I'm using mine and its a bit chilly our or down right cold, I throw an old blanket over the top to just hold in some heat better, careful not to cover the top vents. You runnin' a guru on it? If ya have any other questions feel free to ask away. Good luck can't wait to find out how you make out.