i just use gauze or a paper towel and wrap it around my finger and dig in! really though, if you have had her checked for mites, and it is just dirt, i dont think you should really need anything special to clean them... it just like cleaning out your ears
Our vet actually just showed us on Monday how to do it with a Q-tip. He had a 3-D model of a cross-section of a cat's ear. It's L-shaped, so he said you'd have to really shove and bend it in there to do damage to the canal. He said you go straight down and dig out the wax from the crevices. Looked pretty simple. The hard part is getting her to sit still. It took the vet and I to keep her stationary.
Definitely rule out mites first, but if it is just dirt there are plenty of ear cleaning products for cats out there... I do use q-tips on Oliver, but I've been trained by a vet to do it (used to work in a vet hospital and shelter) - if you're not positive on how to properly use the q-tips with cats, I'd use something commercially made or have your vet show you so youre sure... Ollie's gotten used to the q-tipping - he gets it done after his monthly bath and usually once halfway through the month