I no longer use a smoker, partly on the grounds that I detest breathing in any kind of smoke since I gave up the cancer sticks 4 years ago, and partly because I see no need for it, and partly because what little control I need can be achieved using a mist spray containing water and organic cider vinegar.
This is what I have done with my old smoker:
(sorry, image problem again)
I replaced the bellows with an air bed inflator - half fill with powdered sugar, press button and point upwards through the floor mesh. Treat a whole TBH for varroa in less than 10 seconds, without even taking the lid off.