The simple answer is ‘however you can’.
Some of our customers use our adult size Bass toothbrush to disrupt the bad bugs along the gum line and then follow that by using the smaller, junior size Bass toothbrush to clean their teeth and the hard-to-reach areas, like the inside of the lower front teeth.
To do this, stick out your lower jaw like you would if you had a thermometer under your tongue. Then use the tip of your toothbrush to brush the length of the teeth using small up-and-down motions (exactly the opposite of the normal Bass Brushing Technique, where we go side-to-side). Do this until you no longer feel plaque on those teeth when you run your tongue along them.
We explain more on this in our article How Do I Remove Plaque from Lower Front Teeth?