It's better not to use it, and to do it yourself, consciously. The reason is, if you use a device, it won't train your brain as fast. It's really your brain that you need to train, not the tongue, because the brain controls the tongue. It's worth doing it yourself. I've made use changes as an adult by doing this and also using tongue force, just make sure the position is correct and also train your body posture. It's a lot of work, but it's worth it. Otherwise you'll get substandard results.