Did he have hives, in the same place as the dry skin? If so it could be related, and just need time to go back to normal.
I've used fish oils, coconut oils in the past, and they do okay. What has worked best for my dogs, is adding low sodium salmon to their diet. Just a couple if times a week was all that was needed.
Not all those who wander are lost.
Life is just a leap of faith.
Spread your arms and hold your breath and always trust your cape.
Two things define you. Your patience when you have nothing, and your attitude when you have everything.