This isn't as trite as I presume it's going to sound but the only thing that will restore the fur is time. The question you really need to be asking is "Why is he pulling out his fur?"
More information would help us help you. A general location always helps - the Mountains in Montana, the beach in Florida, the desert in California, you get the idea. What he's eating: brand, how much, how often. How long have you had him? Rescue or known purebred? Have you recently moved? Has he recently been rehomed? and recently in both cases means during the past 6 months more or less.
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“Properly trained, a man can be dog’s best friend.”
Corey Ford .
