Petroleum jelly would be safe to try on the crusty areas as would Neosporin ointment in case its in part due to bacterial infection. Neither will hurt the dog if it gets licked off though petroleum jelly in big quantities might cause some soft stools.
If you happen to use plastic bowls for food and water swapping to stainless may help as some dogs react to the plastic and they tend to rub their faces on it while eating or drinking.
Hope this helps you!
Dog Expert:Rescue, Train,Breed,Care
30+ yrs dog home vet care & nursing, rescue, behavior&training, responsible show breeding, genetics