Sometimes the problem is that the charcoal needs a well vented basket set a little up off the floor of the firebox for the coals to get enough air circulation. The ashes form and then create a blanket keeping out air and insulating the heat from the smoker compartment. I solved that issue in my charcoal burner with a wok similar to this one. I welded spacers on the bottom to keep the wok 2 inches up off the firebox floor. the briquettes burn faster and disappear a little quicker but you get plenty of heat out of them.
You tap on the wok every once in a while to let the ashes sift thru the holes and away from the coals.
You can also make a really good one out of expanded metal .http://www.cabelas.com/cabelas/en/te...set=ISO-8859-1
It is helpful to us when answering questions like this one if you've listed your smokers in your signature. For exampl as I have in my signature. That way we know right away what kind of smoker you have and will have a better idea how best to help you.