The only way I found to regularly get each other off doing this was if I sat straddling her chest/upper tummy, with her face up and me facing her. I think we both found it to be pretty hot and a decent angle for her to get to me. It was also the best angle I have ever found to actually get her off rubbing her clit with just my hand. Just reach behind and cup her pubic area with your hand and a couple fingers rubbing her clit. For some reason at least with me and her it was the perfect angle to apply the perfect amount of pressure with the right motion to get her off.
Just make sure she doesn't mind a face shot or knows when it's cummin.
Our approach to mutual m is that we sit, legs spread, facing each other on the bed. MY partner uses her fingers to play with her clit and I get a great view of her masturbating herself, especially as her fingers slide deep inside her puss. As she does that I gently use my hand pump my cock, and she enjoys watching me pulsating as I slow and quicken my strokes. The aim is to make it last as long as possible and then to come together. We love it!
I like to have him lie on his back while I straddle him in the opposite direction. I have one free hand (and a mouth) that way, and it gives his hands very good access to my pussy.