I use treats to settle my dogs in the bath. They get one treat {a bite, really} when I put them in the tub; one after I wet them; one after I soap them; one after I rinse them… you get the idea.
Maybe you could start by sitting in the bathroom for a few minutes, petting him, give him a treat, and then leave. Next time, put him in the tub and give him a treat. Next day, put him in the tub and turn the water on low, give a treat.... and so on. May be too much work/time/effort. I don't know. But it may ease him into the idea that the bathroom/tub is a great place to collect treats!
Jazz was never a problem in the tub; Keoki started to panic a bit the first two times, but fast/gentle movement, a calm tone, and treats all seemed to help. Now he's just fine in there.
Both dogs still hate it, and run to hide when they see me go into the bathroom with their towels, LOL, but they do fine during the bath.
I use cotton cosmetic pads moistened with bio-groom ear cleaner { http://www.3cdog.com/product_info.php?cPath=26&products_id=1493&osCsid=bbf } to clean the ears.
I also use moistened cotton cosmetic pads to rub down the teeth and gums.