Something you can do to help while not at the guitar. If you’re in a chair put your hands palm down on the arms. Now use your thumbs to lift your hands, so you can move your fingers and tap the chair. Now move one finger on your left hand down to tap on the chair. At the same time move one finger down on your right hand. So now you have one finger from each hand touching. Now as you raise those two fingers up lower two other fingers to touch the chair. I bet your using the same two fingers on each hand.

Put the second finger on your left hand down as you put the third finger of your right hand. Now as you lift them put your first finger of you left hand down and your right pinky. So all four fingers are moving at the same time. Use other combination of your fingers. You can work on this almost anywhere you can tap.