Cat Dandruff
What can I do to help alleviate my boys dandruff. There is tons of white specks and vary in size, and brushes really stirs it up and kind of overwhelms him. It goes all down his back from his neck to the base of his tail. I can also part his fur and clearly see his like... scaly? skin. He is a 7 year old tabby. He has access to a water fountain, gets dry food in the morning and wet food at night. His brother (same age and litter) does not have dandruff. I don't think its his weight, he can still reach everything. Other things that have come up are that he's been having seizures, but when taking him in they found nothing and it would cost me $400+ to test for anything else so I have not yet.
I know he is just so itchy cause he LOVES scratches but also I can see his back twitching all the time. I want to provide him relief fast but also what can I change in the long term to prevent this?