Key/barrel stiff

Today my key(not the card key) is having problems going in and out of the barrel (gets stuck half way) tried my spare key and it's the same, so I'm thinking it's the barrel, I've cleaned the keys and wd40 them and the barrel, and it's still stiff. Now if it is the barrel is it a simple diy job and have you got to get new keys and reprogram them?
 
Perhaps try graphite? I know that for house keys and locks, when they get stiff if you rub a pencil on the keys that helps with the stickiness and smooths out the passage of the key.