When my husband didn't want a shower it seemed to be partly temperature related...he felt cold even if it wasn't cold, and hated stripping off. So I got the room as warm as I could, ran the taps until the water was exactly the temperature he would accept, and once he was standing in the shower I would give him the shower to hold, being very careful not to splash him myself.. I even warmed the shower cream.he would do the job himself, and I would wrap a big warm towel round him as soon as he had finished,and then his towelling dressing gown, warmed.
We did his hair similarly, I could get him to bend a bit, and I would blot it dry immediately, so that no water ran down his body...
He grumbled the whole time, but as long as he was doing it himself, and was in control, we managed...
A good friend sometimes helps him now, and she tells him very seriously that he has to shower because she knows he won't want to smell... She's pretty, and gentle and kind, and he will usually oblige...perhaps because she's female!