SPs providing cimsw are rare because it carries potentially higher risk, may taste bad and represents an extra level of intimacy they may not be comfortable with. It is rarely advertised and not often offered on the first get together. It is certainly never guaranteed. You may just want to ask an SP what they think of it when you find one you are interested in. Some will never go there. In fact, I had an SP (a regular) who offered BBFS but would not engage in cimsw. I decline the BBFS.