3/4" close nipples with 90 ells on the lid also. Conduit lock nuts on both sides of the barrel top to hold the nipples secure.
I use the expanded metal from Home Depot. It cocts about $9.99 for a sheet that's 4' x 24". After the charcoal bin is completed I then use a weed burner to heat the metal red hot and that does away with any and all coatings that may be on it. If you don't have a weed burner you can find them at Harbor Freight or at Home Depot they call them ice melters. If you don't want to do that you can use a plumbers torch with propane or mapp gas to get the metal just as red. Stay upwind when heating the metal so you don't breathe in the metal/coating/plating off gassing.
The early bird may get the worm, but the second mouse gets the cheese.