I unofficially qualified for this group early last month...

[dixiegrrrrl]

17. The trick to the shower

is for a bit cooler water than you are used to
and a bit gentler flow
and to shampoo and wash front body with hand cloth and soap with your back to the spray, using spray only to rinse.
You can also hold a washcloth across the incision line with one hand while rinsing off in front.

the PROBLEM is showering with only one and a half hands, since the affected arm is not going to want to move much initially.
And the same with drying off.
I dried off what I could reach, then threw on one of my many caftans, which dried me off pretty well as I moved.