It's important to note that sensate focus exercises are the main experience, rather than a type of foreplay. The exercises aren't about trying to arouse one another although this might happen. Instead they are about enjoying physical contact and losing oneself in the moment without the pressures that can lead to sexual disorders.
More About Sensate Focus
Sensate focus exercises involve a series of stages of sensual play. When used as part of therapy, couples are encouraged to undertake sensate focus sessions lasting for an agreed-upon period of time and for a set number of weeks, before moving to the next stage of therapy. They are also advised to abstain from intercourse during the early stages of the therapy. A typical first stage of sensate focus exercises may see couples touching all but each other's genitals and breasts. Couples might then incorporate touching of the breasts, and later the genitals, into their sensate focus exercises. Finally, after time spent appreciating sensual touch, the couple can feel free to enjoy intercourse as part of their sensate focus exercises.