This happened to me a few nights ago.
I woke up in the morning about 3 o'clock with a nice woody. What to do? My wife was on her side of our king-sized bed asleep with her back to me, legs pulled up in a semi fetal position. I thought for a while then decided to scoot over and rub her back. Please note that we haven't had sex for awhile. She's not all that into it.
I began to gently rub her back... Up and down, each time going further down. And further up. She sleeps in a short, skimpy nightie. Nothing else. As I moved my hand down I reached the hem of the nightie which lay about half way up her buns. Wow! Skin. This is starting to get interesting... To me at least. On subsequent rubs downward, I would work my hand down and around her nice butt then along the back side of her bare thighs. No reaction from her.
I kept this up for a while, rubbing all the way from her neck, down her back to her butt and around to the back of her upper thighs. Then... I noticed her breathing was getting deeper and 'goose bumps' appearing on her butt. She was obviously starting to wake and perhaps starting to get some degree of excitement.
Then, she rolled over toward me which put her on her back next to me. Legs straight down. This gave me access to her tummy which I started to rub. Higher and higher till I was just under her tits. Then lower and lower to just above her mound... Not skin on skin but over her very thin bed wear.
After a bit, she slowly began to pull her knees up. Then she reached down and pulled her nightie up, raising her butt a bit to release it. Now skin on skin, I continued my rubbing... Up to her tits then down to her mound. After a bit of this she started to spread her knees. Just a little at first. Then finally to a very flat 'V.' Now my rubbing took a different turn. I started at her knee, the closest to me, then down her inner thigh across her mound, lightly, then up the other thigh. Over and over. Down one thigh, across the mound, then up the other side. At the mound my touch was very, very light, almost just a brush across her very short bush. Sometimes at her bush I would go lower across the two bumps of her buns. This has to be man's most exciting play ground... Down a woman's wide open legs' inner thigh and up the other... Feeling the bumps of the mound and the butt.
This I did for awhile. Soon I noticed that, as I passed the mound, my lady's hips would rise very slightly. She's getting into it, I thought. Occasionally, I would stop at the mound and just lay my hand there, not moving. Just enjoying the feel of a closed slit underneath sparse pubic hair and the heat emanating from there.
OK, I thought. Time to get serious. I put my hand on the mound again and, this time with my middle finger, pushed ever so gently. You've got to know that my wife's pussy lips are nice and firm... Like a teen girl who has never had sex. As I pushed, I could feel the outer lips give way. So I pushed just a bit more.. and... my finger slipped through. Both outer and inner lips gave way, my finger landing in her very wet 'love channel.' Then 'Oooooh, Oooooh my God!!!' Came from her lips. I just let my middle finger lay there engulfed in her pussy lips, enjoying the warm moistness. 'Oooooh My God!!!' Over and over. 'Fuuuuck Meeeee!!!' Her hips began to spasm and shudder uncontrollably then undulate up and down, fucking my finger. 'Fuuuuuck!!!' 'Fuuuuuck' Over and over.
What happened next, I will have to leave to your imagination. I can say that my cock was rock hard and dripping pre-cum.