Many children struggle to get in their R sound completely correct.  Here is one way to help them to generalize. I learned this lesson from my client.  How great is that. First we will show you with the Smart Palate then without the mouthpiece.

April; Teaching Syllables for kids with apraxia

I use Visual Phonics (hand gestures) for those needing extra visual cues.
See how I teach basic syllables with "m" as the consonant rotating through vowels.
First video with visual phonics, the second video just showing letters/sounds.
You can purchase Visual Phonics DVD and visual guide booklet at Brigham Young University, author ComD.  Total cost is approx $15.00