when in homes that smokers smoke in. I clean and clean and then I look at my rag or the bucket of water and think if this is the wall, then what does the lining of the lungs look like?
The tar has to come off as you are aware. Painting over any tar is like painting water over oil. There are some good cleaning "cutters" on the market that will assist you. When clean, you then need to apply two coats of quality primer in order for the finish coat to adhere properly.