I had my first ever double tickle session with Mistress Hadid and Mistress Westwood a few months back. They tickled me all over with feathers, fingers, and a few other implements. (I couldn't identify everything because I was blindfolded.) I considered myself only moderately ticklish, but they discovered tickle spots I didn't know I had, and they really got me going. It was an intense but intensely enjoyable experience. They struck a nice balance between teasing and torture, and they improvised a couple of extra tortures I hadn't anticipated. In terms of preparing, just go with an open mind and be ready to put yourself in their capable hands. They are true professionals.