I don't know why you would use both nosebands.
Figure 8's are really only a tool to use if your horse crosses his jaw (and it's better to use a prevention, as once they've learned, there isn't much to cure it) but it should not be used for additional brakes. I used one only when teaching my youngster to learn about contact (he was started western at 3, ridden hunterish from 4-5, and at 6 I taught him how to come on contact/on the bit and used the figure 8 then for a month or so, so he learned to go on contact without crossing his jaw, he is back in a regular caveson now).
Remember that on the track that TBs are taught to pull on the bridle, not back off it. If you can't stop him in a field, ride with shorter stirrups and learn how to use your bridle so that you can use your body to slow/stop, not just get in a tug of war.