I have been blogging about prevocalic/r/ intervention in regards to gliding or w/r substitution
Example: rain vs. Wayne
In intervention for /r/, I teach students that if a /w/ is produced instead of an/r/ as in Wayne vs. rain that the listeners would most likely get confused and think that they are referring to a boy named ‘Wayne versus rain like the weather. I worked recently with a first grade student who used the Entire World of /r/ Playing cards-8 deck set. He usually was apathetic about working on prevocalic /r/, but last session, he had a gleam in his eye and seem exceptionally motivated to work on his articulation. I asked him what the change was and he mentioned that his dad noticed that he was saying his /r/ sound correctly.
What a change in attitude!