(Posted for an unregistered reader)
When we bought homes with cigarette odor: we put out "OdoBan", "removed" all old carpet/pad/fabric & tossed it & "scrubbed" every surface we could access, then we "painted" every paintable surface. Cigarette smoke leaves a film on things, & you can see your cleaning water discolor as you are scrubbing surfaces. Scrubbing seems to be one of the best ways to remove the film (& scent).
In one (odoriferous) trailer the wood paneling was pulled apart from the wall. I put OdoBan on pieces of tissue paper & put it behind the panneling before fastening the paneling to the wall, & put pieces of tissue with OdoBan throughout the trailer, including in the floor vents, (we weren't using the heater.) When we were done I removed any bits of paper lying about & the paper in the vents.
Using an ionizing air cleaner may help. Febreze is helpful in dispensing odors too. Depending on what is under the house, a check under there could be helpful. OdoBan (again) can be placed in crawl space. If the crawl space is deep & has plastic covering the dirt, it might be helpful to replace the plastic...