@imeldahl What /@medic75 said, you can work them both if you have good form. Plank is there for conditioning of the wrists. Make sure you have that down. I'll edit the post to clarify that in a bit.
@wicowgirl4christ Have you tried chin up negatives?
Chin ups usually take a little more time compared to the rest. Stay positive! If you have an assisted chin-up machine that would be helpful too. What rep range are you working in?