Mom's muscle tremors makes it difficult to help her with bathing and hygiene care. Any tips where her pride and dignity are still respected?

Mother is diagnosed with late stage Alzheimer's Dementia along with Parkinson's. I am my mothers pimary caregiver and "P.O.A". With her parkinsons muscle tremors, her left arm and hand is worse than her right side. When I help her shower while sitting on her shower chair, her hands and fingers tremor very quickly and remind me of "lobster claws", opening and closing, like pinchers. I suggest to her that she holds on to a clean dry wash cloth while I am washing her back , etc. that she is unable to reach when showering. That idea only lasts a minute or less, then it falls to the shower floor. She insists on showering most of her body that she can reach while stting safely in her shower chair. I greatly encourage and assist her as she requests, but most times her "trembling", shakey hands and claw like finger actions makes it difficult for her at times, then her breathing and tremors get quicker when she gets aggravated herself.
Has anyone else experienced this kind of situation when helping one with Alzheimers Dementia Parkinson's disease with bathing and hygiene care?
Any suggestions or tips are appreciated as her pride and dignity are greatly respected.