As someone who has a mild prolapse I have been to the physio about it and the advice that she gave me was, to imagine you are sitting on a silk hankie and you are trying to "suck it up" and hold it before you let it go.
She said it is the visual she gives the older ladies so they can almost picture the hankie and do the exercises properly.
As for the wetting your pants, this is the exact reason I wear pads most days. Rather that than an untimed sneeze catch me by suprise!