Its probably not the shampoo.
In fact - when I asked my son what he has a problem with...he would list everything from 'water' to the 'shampoo' to...well...everything that basically meant I would just end up not washing his hair at all.
Looking back - I know when it started. Because he used to be fine with me washing his hair...water all up in his face and everything! Then he got the chickenpox!...and thats when it started. Most of the pox were all over his head.
Now - we respected this. Not a problem. If he wants to look like a littel urchin child - okay...his body, his choice.
And then he got lice. Which actually has nothing to do with him not washing his hair by the way (I nanny schooled children - you know how that stuff spreads like wildfire in schools! lol). We had to do something as they were starting to infect his skin around the bottom of his scalp
... We had to wash his hair...they had to go! lol (this wasn't a forced thing - we talked a lot about it and he wanted them gone too!)We got this.
And since then he has been real good about us washing his hair. I get to do it at least once a month now! lmao And water doesn't get in his face. Sometimes in his ears which he doesn't like but it no longer sounds like I am slaughtering him in the bath any longer! lol (and before the shampoo cup - he wouldn't put his head back either...for some funny reason, when we got that special cup - he did!...He would sit towards the tiled wall and put his hands on the wall like I was a cop frisking him lol - and tilt his head back so I could rinse. We even condition now! lol) (his hair is super long though as well - and super fine blonde -its needed! hehe)