If this smoker is what I believe it is, it is similar to a UDS. If it is getting too hot, it is obvious that you may have too many coals lite a once. What you are going to want to so is use the minion method. Basically have an amount of coals in your firebox, the you will want to light a vastly smaller amount of charcoal, once fully ashed over, you will want to add this to your cold charcoal. Once the charcoal is added to the other pile you want to cover this and keep checking your temperature. Be careful not to keep opening the top of the smoker/ grill, this will cause extra oxygen to enter the chamber and ignite more charcoal, which is exactly what you dont want. You want your charcoal to burn as long as possible and a sustained temperature. I would recommend between 225° and 250°.
You may want to invest into a Maverick Thermometer. You will be able to keep the temperature of you meat you are cooking and the grate level temperature at the same time.
Brinkmann Trailmaster Limited
Brinkmann Vertical Charcoal Smoker
Weber Spirit E-320 Propane
Weber One-Touch Silver 22-1/2"
Weber Jumbo Joe 18"
Weber Smokey Joe Gold 14"
Fully Functional UDS 22.5" Dual Layer