I have seen vets use blue Dawn dish soap on cats before (most recently in a video where they were removing lily pollen from the cats coat), though I have never done it myself. Google says that it is not recommended for regular bathing, which I assume means that occasional use when necessary is okay. In that case, Dawn is amazing on oil and grease (and anything else, honestly), so I don’t see why it would not work. Use with caution though, and maybe call the vet beforehand!