I am sure you'll do much better with Charcoal vs Lump. Once you get to temp with the coal, I like to close the draft on the fan at least to close it one line. Also, you dont have to fill it with briquettes. A little goes a long way with these cookers.
MJH From Backyard Bomber BBQ ---- X 2 Junior & Stretch
22.5 Weber Kettle
Wine & Swine