Have Cat Questions? Ask a Cat Vet Online.
Hi, this is Dr. Gabby. I would use a dish washing detergent, such as Dawn or Ivory, to remove the grease.
The dish washing detergent seems to work better than shampoo to remove grease and dirt.
If you can not get his tail wet I would use sensitive skin baby wipes. That is not as good as dish soap but should get some of the dirt off.
I also really like "Quikclean waterless shampoo" You can buy it online quikcleanhttps://www.vetdepot.com/quikclean.html
Does that help? Do you have any additional questions?