The images are gross in cognitive sensitization. Also, many people don't believe there is a strong relationship between fantasy and behavior. Just because a sexual fetish with bras has been associated hundreds of times with imagined vomit, it doesn't guarantee that the attraction to real bras will be extinguished. The role of suggestion is unknown in most self-help methods. The research centers on covert sensitization.
More research is needed with the other covert methods.
The results are promising enough to try these methods, especially if the approach has an appeal to you and is believable. Remember the research thus far has been done with long-term clinical disorders, not ordinary problems. Additional readings Cautela, J. R. Covert conditioning. Academic Press, 1971. If a behavior yields no pay off, it should gradually stop, i.e. be extinguished.