What's wet and wiggly and can hear?

Emerson has done really well since having the tubes put in her ears. She holds still for the trice daily ear drops and even holds the box that the little bottle of ear drops lives in when not in use while getting said ear drops. BUT she fights fights fights when it is time to wash hair. She is supposed to get fitted for ear plugs at her follow-up appointment with her ENT, Dr. H., but that doesn't happen until the 29th. In the meantime, I am doing the cotton ball/Vaseline thing, but it's not working. The cotton balls always fall out and she fights if I try to hold her ears closed. Have any of you ever tried to hold on to a slippery wet screaming wiggling toddler while rinsing hair and holding the ears closed? My third nurse hand is fairly well developed, but even I can't do this without both of us being reduced to tears. The other day, I considered just not rinsing the shampoo out of her hair. SERIOUSLY.
Other ideas I've had and already considered:
1. NOT washing her hair until the 29th, but I am afraid that her school may not let her back in after a few days of this.
2. Trying to recruit the cats to groom her hair, after all, they do their own all the time.
Any other suggestions anyone may have, please place in comment section. As you can tell from my other ideas, I'm getting desperate.