Candice, here is an article on how to show
chicken that you might find helpful.
What I found that you might be interested in is the part about training the birds.
The article suggests using a gentle shampoo with a rinse of
apple cider vinegar to get the shampoo residue out.
https://www.wikihow.com/Show-Chickens
On another website, there was a suggestion to use baby shampoo.
I also saw this product being recommended:
All Natural Murray's Best
Chicken Suds and Conditioner
https://www.mcmurrayhatchery.com/all_natural_murrays_best_chickens_suds.html