I have had no troubles controlling my temps, however I use my cookers a lot more than most The best thing I can tell you is to use your cooker a ton, once you learn where it can get to in regards to emps, you will know what you can cook.
Jim, has great results with low temps, I think because he uses briquettes.
Any pics of what you are trying to do?
I think two of my cookers, have no control over the vent ( no just one has no control, I dont use the other one) and the rest all have some kind of control.
Just leave the vent open, and regulate temps with the intake of fresh air.
See what