Here are some links with more information on Tongue Thrust. For the most effective correction, Dr. Bibby recommends working with a trained Speech language therapist who has an interest in Tongue Thrust, such as Jennifer Moll in Trail. If that is not possible there is a list of exercises (scroll down on the Resources Page) that could be worked on at home, but this requires consistent practice.
This link below has a good FAQ and shows a sample exercise. This program can be ordered online.