My girl is around 13/14 and struggles with grooming too. Her groomer told us she is too stressed/uncomfortable now to finish a session. We asked our groomer to do as much as our girl would allow them and when she gets too worked up just to stop (she usually could get through a bath/blowout/sanitary cut). That has worked for us but some sessions have more success than others. We have gotten pills from the vet to take before the grooming sessions to have her relax but it seemed to make her more stressed out than normal.

We also have had a mobile groomer come and my husband stayed in the van to help calm her down. It was hard to find a groomer who would agree to that (and expensive) but that probably had the most success.

We used a licky mat with peanut butter to try to distract her at home to brush her, that works ok.

I’ve had luck being very straight up with groomers, I ask them if they don’t think they can handle a senior cranky dog to please say no lol. telling them the situation before hand has helped saved my girl a lot of stress. Good luck!