Mistrix Sade in NYC is excellent at smothering- I've seen it in-person.

I am not located in NYC but tour the city twice a year and consider full-weight smothering to be a specialty of Mine. It seems so simple but really requires a great amount of intuition and ability to read body language.

I think the question asked above re: what makes a great facesitting session for you is important and valid. I personally prefer to instill fear and panic during smothering by watching My subject closely and going just a second or two beyond the point where panic sets in. It really makes you appreciate that gasp for air so much more!