My baby had black crusty spots on his tummy near his penis. I thought they were moles but the Vet just peeled on off and said an infection due to moisture. The vet didn't test if it was bacterial or yeast but recommended to clip him very short in that area. I had his groomer 'shave' that area.
I found a site on the internet that recommended using dilute povidone iodine because it is safe if they lick it. It has helped to remove the crusty spots and keep any more from developing.
A Simple Remedy to Treat Dog Skin Infection