How can l communicate better with my Grandmother with dementia?

I take care of my beautiful 86 year old Grandmother, she have dementia, I am her caregiver, without any help of the family for 3 years, my sister who live in Florida is the only one that give support over the phone as much as possible. However the problem is Grandmother is very demanding, in a great deal of denial when it comes to toileting issues, her timing is off when need to wipe, I do know she not understanding, it can be messy at times, if she not receiving any tissue, she yells, irritable and cries, at times used her cane to hit me, throw her stool at me. Therefore I distract her by getting her to read the bible until she evacuate completely, Really my Grandmother is a sweet beautiful kind woman, full of smiles with a big heart, and very soft spoken. My sister and I loves her very much, we make sure she dress to kill every day and hair in place. Then we make sure she stay on top of her exercises, walks, take stairs not the elevator, everyday plus physical therapy as much as possible and more. Therefore we keep her busy with the church and activities she always on the go. If i can learn how to communicate with her a little would very helpful. I can't let her down, l made a promise to my Grandmother and l am going to see her through, because who she is now is not her fault, but she will always be our beautiful Grandmother, she name me after her. Please if anyone can offer some advice would be helpful. Thank you for listening.