Its hard well at least for me too. I have the same conditioner for Mimi due to her allergies and all and she refuses to sit in the tub with it on. She's a big whiner and all she does is scream and cry and it gets louder and louder. My vet gave me a shampoo that I had to leave on for 10 minutes
I told the vet I cannot keep a condioner on her for 2 mins now 10 mins for this. I just stopped using it. Maybe you can wrap him up in a towel and hold him?