You may wish to take a warm, damp wash cloth with a little soap and try to clean the area as best as you can....dry the area - Then you can sprinkle Arm & Hammer Baking Soda onto your cat's fur and rub, then comb or brush it through and out....This product is non-toxic, so it's safe and and will not traumatize your cat.
I'm sorry for your cat's condition, but he is certainly in the best of hands. You're a good mom!
My very best to you and your cat.
Please take care.
Peace, Love & Happiness,
The Mystic Wave
Adding to my post above.....just be careful to keep the baking soda from getting into your cat's nose and eyes.
Thank you for accepting my response, it's deeply appreciated. You're very welcome - and I do know your kitty means everything to you. My thoughts and prayers are with you and Charlie. If there is anything else we can assist you with, please do not hesitate to let us know.
Please do take care - and great big hugs and kisses to Charlie.