I always fill mine up, then after the cook shut it down and reuse what is left in the basket for the next cook. Mine will go 16+ hrs on a basket full of lump, without stirring it. Try some lump and see how that works. I would leave the top vent open no matter what and regulate the air flow with the bottom vents. Mine also seems to work better if you catch the temp on the way up rather than lot it get hot and try to bring it back down. Good luck!
UDS, Mini-UDS, smokey joe, gasser, 3 pie irons, and a weenie fork.