My wife and I have a foreplay technique that we call an 'L7'. This is basically a masturbation variation of a '69'. We lie on our backs, foot to head on each other's right side. Then we each put our right leg over the other's chest, so that our right hands have free access to the other's crotch.
We were doing this last night and were still in our bikini underwear (hers were white cotton and mine were powder blue microfibre). We were just gently rubbing each other through the material. She uses several techniques with her fingers and had been rubbing the wet spot in my shorts with her index finger. She then traced her finger down my shaft and started tracing around my balls. Her finger would go across the point where the shaft met my balls, down the leg opening, accross my crotch and back up the other leg opening. After she had done that about three times, I suddently came! It is the first time in my life that I had come without direct stimulation on the head of my dick at the moment of climax.
The feeling of the cum squeezing between my cock and the tight bikini was also amazing. I've never felt that before, because even though I've come with bikinis on, I've always had my hand pressing against my cock through the material. I'll always remember last night because I doubt it will ever happen again like that.