Just a point, in very turbulent air rather than trying to chase altitude and heading, concentrate on holding ATTITUDE and let the A/C wander a bit if you have to. [just noticed SSD already said this
]
I've had a few VERY bumpy flights in VFR and IMC, worst was when ATC vectored me into some rising cumulus while on an approach, it got wild and it was quite a job trying to follow their instructions. Another time was coming back through a mountain pass at 8500' into the LA basin. vis was crap, and it was bouncing all over the place for over 2 hrs. Still there was two of us pilots onboard so we shared the workload, one operating radio etc, the other flying. When the PF got tired we swapped roles, the RH seat guy would take the controls and the LH seat would take responsibility for the RT / Nav etc.
Cheers
EA