Tenant smoke in garage and the smell already penetrate drywalls. Any suggestions of getting rid of the smell without replacing drywalls?

Kilz primer on walls and ceiling. Ceiling concrete floor after cleaning (you can google many products). And hours and hours of an Ozone Generator (I bought one for $85 on Amazon). 

I've read Ozone generating machines can help, but have no personal experience with them.  Can you expand on how much it helped after many hours?  For example, would it only work on a light smell from an occasional smoker compared to a heavy smoker?  Also from what I read, you may need a larger ozone unith than whay $85 will typically get you.  We used Killz to paint the floor under the carpet after a tenant snuck a dog in that urinated everywhere and it seemed to help.

Thanks guys! I tried Zep Smoke Eliminator spray from lowe's and it seems to be working. I sprayed 2 bottles directly on the dry walls and ventilate the garage for the afternoon. There is still some smell remaining, but almost negligible. The next step I am going to paint the entire garage. I think this would solve my problem. Thanks again for your comments!

@Lily Liu try Ozium

Decades ago I read in a newspaper that putting baking soda (sodium bicarbinate) in a smelly frig , left in it for days, will get rid of smells. Hence, have tried the same thing on floors that had been urinated on, & after months of baking soda so laying, any smell had gone away. Hence, find places in garage to secret baking soda, even drilling holes in dry wall, that you pour baking soda into. And this may help with your smell problem, in reducing it.