Another thing is to definitely use lump over briquettes. Briquettes burn longer, but they make a ton of ash. It builds up in small offsets and chokes down the fire, causing you to have to use more fuel to get the temp back up.
Lump burns very clean. Just dump a chimney full unit coals into your firebox, then a chimney full of lit on top of that. This should get you a good while before you have to add fuel. Start with the air intake almost closed and gradually open it a little at a time, to reach your desired temp. Later when it drops, just open the intake some more to bring the temp back up. When you reach a point where opening the intake will no longer raise the temp, then its time to add more fuel. Just dump in another chimney of unit lump. Leave the intake open until the lump catches good and then close it as needed.
I know that sounds like a royal pain, but with a little practice you will have it mastered. I had a Silver Smoker too. You can make some fine Q with it, its just a little more work than say a UDS or WSM.