I think bathing a dementia patient is a pretty common problem area, and I don't remember seeing a post on this hint before. It was suggested by our geriatrician; tried it for the first time yesterday and it worked. This is a replay:

--I washed DH's hair in the kitchen sink with the sprayer, since doing the hair and body at once are more than he can take.
--After two shampoos (DH had pulled off the visor I use to keep water out of his face) he was preoccupied with drying his face with a towel.
--I took the sprayer and proceeded to wet his tee shirt, pants and even athletic shoes!
--I said "OOPS" -- I got you all wet!!!
--We proceeded upstairs to the bathroom, where I turned on the shower while helping him remove the wet clothing, shoes, etc.
--He then agreed to get into the shower and things proceeded normally.

For some reason, he thought he was responsible for getting everything wet and kept apologizing. I took this as a good thing, since one can't be apologetic and combative at the same time!

Not sure why bathing is such a challenge. My dh will shower if I nag him, but he gets all defensive about it. But, when he emerges all clean and smells so good I make all goo-goo over him and he usually warms up and gets over his mad. Now, brushing his teeth is another matter and I am not at all interested in sticking my fingers into his mouth. That's my story and I'm sticking to it :-)

My Dh will get in the shower with some coaxing but will just step over the threshold and not get all the way in. He will say that he is in and I try and prod him until he gets mad. Now using soap is another matter!
As far as teeth they get a very quick once over and then he scrubs the sink with this brush....yuk!
Shaving is getting more difficult everyday. He can no longer shave himself but he is extremely sensitive about anything touching his face. He whines and turns his face while I am trying to shave him. I only do it every second day anymore because it is getting to be a real hassle.