The TECHNIQUE I suggest works best is this - not hard and you don't need doity pics.

She is face DOWN (that means you can't see her titties) over some pillows so her bum is sticking UP a bit. Her legs are APART.

You are either on your side or semi - face down also between her legs. When I say face down I mean you are looking at her not the ceiling.

With the two of you so positioned you would have to break your arm and turn it 180º for you thumb to be pointing the WRONG way. When you insert your thumb the thumbnail will be UP and you will be pushing down. Like I said to push up in that position wouldn't make any sense. You need some power and a position you're going to be comfortable in 'cause she's going to want you to do this until she can't take any more. If she's young, horny and good shape that could be a long time.

OK, you have inserted your thumb - and again I suggest you do this like it is extended foreplay not just booom and start G'ing her. That can come later at the right time but just learning, BOTH of you have to be turned on. So... you've inserted your thumb all the way. Now just start to push DOWN. Down will obviously be towards the mattress. Do not be too rough right away. Move the thumb around, back ad forth, side to side...make the movement kind of rhythmic until you see her becoming more and more aroused. She may want you to stop because it feels, initially like she has to pee. Forget that. She doesn't. Just keep up that pace or go a little faster. You'll know when she's about to have her first orgasm like this. It'll be VERY obvious. As she approached orgasm start to move your thumb back and forth in a parallel motion to her spine and then get quite rough. Go fast and hard.

When she comes it will feel like she's just been hit by a train. Keep going until you can see she's run that orgasm and is running out of air. At that point stop for 15 seconds - 30 seconds - just enough time for her to get some good air back in her lungs. Then start again. You can start again at almost the same pace you were rubbing just before she came the first time. Within a few seconds she will cum again. For the women who have never had this done to them it completely freaks them out. If they have never had multiple orgasms before and you show them that YOU can make them cum, hard, over and over again, you are a God.

One thing that will probably happen with some women who have just discovered that their SO can do this to them is they get scared. All of a sudden THEY are no longer in control of their own body. They can NOT stop cumming when you do this. I've seen them try. I've told them, "Do everything you can NOT to cum." and they can NOT stop. I suggest you stop for a bit if they do get scared and just reassure them and cuddle for a bit and then continue until they are completely shatttered.

They will probably feel a bit weird the next day. Many women have "wobbly legs" the next day. Many will have spontaneous orgasms the next day. I'm serious. You LOOK at them over breakfast and wiggle your tongue and BOOM they have another one right then and there. THAT scares them too but assure them it will pass. It's like the last couple of mortars going off when you blew the ammo dump the night before , is all. I found that women who are about to start their period get sore if you do it TOO much or you're too rough. Probably too much fluid and blood engorgement in the area so give them a few that way if you want but don't be too rough if she's about to start or she'll feel like she's been booted in the uterus the next day and you don't want that.

Does that help?