I know people that just hand there dog an egg, and they have the fun of cracking it and eating it. A bit messy, granted. I just grind up the shells in my hands (raw) and put them in a bowl with the rest of the egg,(and then wash my hands! Yick!) and sometimes yogurt, olive oil, nutri-stat, or by themselves.... my husband uses the blender. The film on the eggs has not bothered anybody here yet, but do whatever you feel comfortable with. We have our own chickens that are kept clean and humanely, and the eggs are organic. I feel very comfortable feeding the eggs to my pets raw. For ferrets (just so you know... like you care) only give the yolk, and cook the shells due to biotein (spelling on that?) ... it is fine for dogs and cats, however.
A bit of animal fat once a week can help the coat, as well. Organ and tripe is good to give here and there to see some improvement as well. Flax seed oil is good, but you have to keep it cold, use by the experation date, and make sure that it is sealed when you get it (it is nasty stuff if it spoils) ... the omega -3 s are good for the dog.
FISH! Fish is REALLY good for the coat. Feed raw. DO NOT FEED SALMON. We feed catfish raw, and get it for a really good price.