The amount of stimulation can be decided on the density of each moxa cone. When you put too much pressure in rolling moxa cones, they will have more density and burn longer with more heat. When you use light pressure, the moxa cones will have less density and will burn shortly with mild heat.
The size of moxa cones is important to produce the effect you want to produce. For the patients who are weak, chronic and deficient, mild stimulation seems to work better. The sensitivity to the heat is various depending on people. If a patient is too sensitive to the heat, I would use just one loose moxa cone. After you apply a moxa cone, you may want to ask if the patient feels the heat. Facial expressions on the patient will tell you with ease. If a patient does not feel heat, stimulation and heat may not be enough, and you may need to roll cones with slightly more pressure. However, be careful when the patient has diabetes since they tend to have insensitivity. This is why you should learn to roll moxa cones with your fingers instead of using small boards. If you want to be a good moxa therapist, you will need to train your fingers to roll appropriate moxa cones you need.
I recently had a patient who had zero range of motion. It looked like the right shoulder became glued to the side. The patient could not move the right shoulder at all. With one treatment, the patient regained the range of motion by about 70%. I used cones of slightly more density with acupuncture needles. I had another patient with pain I was not successful with. The pain location was deep beneath the muscles. I knew I had to use the continuous burning moxa cone technique which was to add cones on burning moxa cones to increase heat and stimulation. Since she was sensitive to the heat, I had to use loose moxa cones with less density. As I expected, the outcome was not satisfactory. In this case, there will need to be more frequent treatments, probably everyday, not every week. Otherwise, you would not be able to achieve desired outcomes. Also, you will need to start with as little moxa cones as possible in the first beginning, and then increase the size or density of the cones by the time the patient becomes used to the heat.