Being I just blast it for metal purposes I dont have anything attached. Many though get fancy with it. Ive seen something as simple as a swaying hinged piece that attaches to the back so you can reduce the air flow. There are those that increase the air flow by adding extensions to the back for forced air inclusion.
This guy got a lil fancy with the back end piece twisting down and up for the vacuum air flow...
There is also another option of the "side arm" burner which uses the three way coupler. The air comes from the top. This though can be more difficult to acquire because most big retail hardware stores dont always stock that elbow reducer. I found one though at a tiny old town hardware store, those guys never disappoint.
Whats nice about that lay out is it lends the idea of using a MIG welding tip as your gas port instead of using a simple drilled hole. So between the gas port size, gas pressure, and air flow you can easily adjust your heat output. The metal forging community isnt too big when it comes to internet info but there is enough out there to give you the info you need.
Oh and use Black pipe not Galv. I see you had a Galv trash can. Eventually it will all burn off but still Zinc fumes are not fun things to inhale. Zinc will burn off galv stuff very easily its better to just avoid entirely. The main body of the side arm burner is galv but that part of the assembly doesnt get hot enough to matter, so really just focus on the areas that do.