I have a GOSM prop smoker and I'm sure the dial on the MB is just as crappy (read, lots of wiggle when moving left or right). At first I just pulled it off when I smoked, but then replaced it with a generic knob with a set-screw.
What will really help is adding a needle valve in your line between the tank and the smoker. It allows a much finer tuning of the flame than the control knob. I normally open the needle valve all the way (look at the flame and you will find the spot right where it begins to adjust the flame), then adjust my control on the GOSM to around the temp I want, say 225. After, I find the sweet spot, I will only use the needle valve to adjust the flame and I can keep that at no more than +/- 5 degrees of where I want.
Keep in mind, vertical props are a pain on windy days and can vary the temp by 20-30 degrees with each gust. I normally keep my vent almost closed, and I have bricks that can block the wind as needed on the bottom.