Anytime your chin gets into a mess, be it stains from a toy or treat, or nutrical or poop gets stuck in their hair simply use a warm damp cloth to gently wipe the mess off of them. Then thoroughly dry the chin, making sure to get all moisture out of the fur, as leaving the hair wet could lead to fungus growth. Make sure to give a dust bath too, as most stains will come out with several dustings and do not require the chins coat to get wet at all.