How to deal with smoke-stained walls/ceiling

[Nathan Gesner]

I just bought an apartment complex. One of the units was occupied for nearly 30 years by a chain smoker. He had a stroke one week after I bought the place and his family is cleaning out the apartment. 

SIDE NOTE: This is why you should always have a reserve! I bought the place June 1st. This guy had a stroke one week later. Two tenants moved out in the middle of the night and one of them didn't pay any rent for June. I'll file for eviction on two more tenants next week because they are behind on rent. That's five units out of 11 that will come vacant one month after purchasing. Every unit needs cleaning, paint, and at least minor renovations. I'm projecting putting $6,000 into them. If I weren't prepared financially, this would kill my entire portfolio!

What is the best way to deal with walls that are heavily stained by cigarette smoke? I've washed walls and painted with Kilz on other units and it was hit-or-miss. This is the worst I've ever seen so I don't want to waste time and money on something that won't work.