Gymgurl, my wife says that when she is ready to come she can flex her inner walls, and intensify the contraction and this causes her to squirt.
You must have good control over the vaginal muscles to do this. Have someone? with you on your back and legs up, rub your G Spot, start slowly, pick up tempo, as you practice squeezing internally. You will find the speed you need, this will take some practice, but I'm sure you will have no problem getting help.
But these must be vaginal orgasms, not clitoral.