Hi Bruce,
It's not easy and normally takes a combination of several things for the best results. If you are doing a complete rehab it's much easier and your chance of success is much increased. Remember what the challenge is - smoke goes everywhere and sticks to everything in the house. The longer they smoked in the house the harder its going to be and the more work involved. Here are a few steps to consider, if done correctly will work to remove most if not all smell.
Get a ozone machine (hire a fire damage/restoration company) to start with which basically sucks the oxygen out of the house which kills the bacteria that causes the smell. Be sure to open all cabinet doors if you do not plan to replace them.
Rip everything out of the house possible depending on the extent of your rehab i.e. carpet, padding, cabinets etc. The more you can remove the higher chance of success.
Kiltz (primer sealer) everything including the floor. This must be done thoroughly to ensure success
Call your friendly HVAC repairman and have the central blower unit squirrel cage removed and cleaner and the coils. You will also need to have ALL the air ducts cleaned and sanitized or replaced but may be a huge costs to replace.
Anything not removed from the home such as hardwood floors, wood cabinets not being painted will have to be cleaned thoroughly.
If done correctly, you will be in pretty good shape. The less of the steps above you can accomplish the less chance of success.
Hope this helps.
Tim
