Ex: Practice changing chords. Let your right hand rest.
Practice different combinations. c to f , c to am, c to g, etc .
When you can do the left hand chord changes without hardly even thinking about it, and not loooking at the guitar, then your're ready to try the right hand by itself.
When you practice the R. hand, mute the strings with the L. hand. Make sure you are keeping an even beat with a metronome. When you have mastered the correct strumming rhythm, then its time to practice with one chord and that rhythm. Then another chord and its rhythm.
When that is mastered , then try it all slowly.