Hold one arm out with your palm down and with the other hand push all five fingers up and back to stretch the flexor on the bottom of your wrist
A two plane swing requires you to start your downswing with a hip bump forward and then arms pulling down, which relies a lot on having good timing
Use a two by four on the ground to represent your impact position and practice slow swings working on getting the clubface to come down square to the two by four with your hips opened, your left arm high and your right arm low