dandruff and bad coat

Question
I have a 14 yr old male cat who has had diabetes for almost 10 years.
He isnt a very clean cat and I can only assume that it is because his fur doesnt taste too good with all the dandruff he has. My vet says his skin can be irritated by the diabetes. He is also famous for large knots in his fur. I cant find time to give him proper weekly brushings but I try.
My question is this: Come summer can I shave him and do something to moisturize his skin somehow to bring back the luster that his sister has on her coat? She has a beautiful sheen to her and grooms regularly. Please help!  

Answer
Yes you can shave down a long haired cat.  Many cats that are matted require a sedative so it may be best for you to have this done at a vet's office. Be careful not to skin him or if he goes outside he will sunburn.  There are many types of coat conditioners that are pump sprayed on the coat.  Look for one with lactic acid or something called alpha-hydroxy acids.  This will help prevent the flakiness.  You can also add Omega 3 fatty acids (available from your vet as a food additive) and that will also help restore the luster to the skin and hair.