Yep, I have trouble with ds as well. I try very hard to get him to look up so that I can pour water on his easily shampoo'd head (I say easily because he doesn't mind having it lathered, he just hates the water part). I don't blame him because, if it's done wrong, he can end up with soapy water in his nose and mouth. Bleah!
I haven't tried the mirror... that may be a good idea with lo. I've done the facecloth bit but water still goes in his eyes. I just try to be quick about drying his face as soon as it gets wet and, most of the times, I can get him to calm down.
I've also had dh come in and sing to him and, while ds is looking up from the bath, I rinse his hair. DH isn't always available at night, though.