how to make fur look greasy/oily?

this is an odd question i know but!

i have a bird character that's kind of horrible to look at on purpose. i'm considering making a partial of him. part of his design is that his feathers look a little bit oily/greasy.

is there a way one might do this without it being a bit of a mould/bacteria hazard? like using a specific type of fur/product?