A golfer's assistant is called a caddy. A caddy is paid by golfer. Most professional golfers have caddies.
A 'scratch golfer' is the name given to a golfer whose handicap is zero.
An Expert Aviator is called an "Ace".
A bully expert is called a bullnation
A cultures expert is called an ethnologist.
an expert on China is called a sinologist.
what ia an expert pilot called
Don't know the origin of the word, but a snake expert is called a herpetologist.