I don't know if this would help you. I have RSD in my neck, shoulders upper back, left arm, hands, and feet. I don't have a lot of range of motion. Can't really get my arms up to wash hair in shower. Shower also hurts me.

A friend installed a "shower massage" head on an extra long hose to my shower. He even made this PVC pipe "drop" so that the shower head connects a couple feet lower than normal, so I don't have to struggle to hang it up or get it down. I sit on the edge of the bathtub, lean over, and can use my better hand to hold the shower massage thing and do my hair that way. I keep my hair fairly short, which also makes it easier.

I also dilute my shampoo to make it easier to rinse out.

I sit on the edge of my tub to wash the lower part of my body also, and use the shower massage thing on the gentle flow to rinse. Then I stand and soap up the upper part, and use the hand held shower massage to rinse. The spray does not hurt as much if it is close to the skin.

I did try three shower massage things out from the "big blue box store" till I found one with a super gentle spray.

An old trick for getting soap out of hair is a couple tablespoons of vinegar in a quart of water as a rinse after shampoo. Then rinse again. I have used this a lot with one of my dogs who has long, thick hair.

I don't have experience with dry shampoo.... sorry!