If you are getting soot, you have a burner/regulator problem. The soot deposits are from a flame that is not burning hot enough. You should have a very fine yellow/blue tip on your flame that is under the pans. If you look, you will see a large yellow flame which is causing your soot.
 
You will need to adjust your regulator. If it is like the one on my rig, just above the temp control knob there should be a large screw, you need to remove the screw. Once the screw is removed, you will need a narrow flat head screw driver to insert in that hole where you removed the screw. In there is the adjustment screw for your flame. You will need to GENTLY turn this brass screw while the burner is lit. Adjust until the flame is bright blue with very little yellow. The more yellow flame the more soot and less heat.
 
And then we have your burner, where the flame comes out, it should be lit all the way around. If it is not, call All American and have him send you out a new one. They cost around $8 if you do not have a warranty. I have tried to source these parts locally, other than the thermo coupler none of these parts are available. I would suggest getting at least one new regulator and burner assembly just to cya.