I use only use lump and can usually set the temp. and forget it for atleast 12 hours. Just light half or less of a chimney and let the temp slowly close to the set temp and close the ball valve until you see the temp start to settle down. It should remain steady for a very long time.
The only time I have problems holding temp if I start to much lump at the beginning or when I had my webber lid out of round and it leaked air really bad.
1 Raspberry PI Heatermeter homemade temp controller UDS