I have my boys on Omega 3-6 oil from the vets, which gets mixed into their wet food. (I also have to now add some "stinky" wet food to this or they won't eat it. )

I used to use a clean dropper bottle with canola oil in it(olive oil is even better, and NEVER use castor oil) - and would put literally ONE drop on the wet food. You use dry food only?

Try introducing about 1/8 of a 6 0z can of wet food just once each morning, with a bit of warm water and maybe a drop of oil.

Even adding the wet food may help hairballs pass through him more easily.

Hope some of the ideas here help.