Kindly suggest what should be done to make my golden Retriever fluffy?

2+ golden retriever is agile, active but is not as fluffy as the general goldens are. He is choosy on foods and develops one of his new pampering ways to eat. He likes home food only, however we are trying to make him eat the dog food but he will not eat till the time the dog food is served with milk. His behaviour is like a typical Golden who is over affectionate and friendly. Kindly suggest what should be done to make him fluffy. Also kindly tell till what age does the Goldns grow?