fordman, lump will burn hotter and bricks will burn more even and longer. I mix about half and half, (experiment with your drum as they act a little different), do some cooks and see what works for you and stick with that combination. Some burn all lump, some burn all bricks...just experiment. Either way will work just fine. 10lbs or maybe a little more should do the trick. Add plenty and see how much is left for the next burn. A little too much will keep you from fighting the fire in the latter stages of the burn and anything left over will keep just fine for the next cook. You will be just fine. Have fun and keep notes.
my avatar swiped fatties from the plate....look how sorry he is.
NB Bandera with mods
Weber 22 .5" x 2, 26.75" x 1
UDS x 3
Created "The Great Spam Revelation of 2011."