Hi there,
I think to answer this question you have to have a very good grip of what happens physiologically just before and during the second stage, once you know that then you understand what needs to be done in order to facilitate a quick easy (and one where you don't push) second stage.
Humans weren't designed to forced push their babies out (as Western women do today) and a lot of myths surround this (including "the urge to push" and the fact that you have to progress to 10cm dilated in order to birth your baby). Actually - as a species - we are designed to spontaneously open (dilate and also perineum relaxation) and, without conscious help from ourselves, our baby is designed to be rapidly propelled down the birth path. This has been termed "The fetus ejection reflex" - FER - (originally by Niles Newton and latterly Michel Odent). The FER is however a bit like the holy grail of birth these days and rarely do women experience
how birth should be as they inhibit the delicate chain of events leading up to it.
Basically for the FER to occur oxytocin needs to be flowing freely, the women shouldn't feel observed, she shouldn't be too cold, the light shouldn't be too bright, she shouldn't feel afraid and most importantly of all her neo-cortex ("the new brain" - the frontal part of a human's brain that differentiates us from other primates) should under no circumstances be stimulated (i.e: she should be functioning with her older primate brain) - the biggest cause of neo-cortex stimulating is language - the the first and biggest rule is "NO TALKING" (by anyone, saying anything) the second rule is that the woman shouldn't rationalise anything or try to control anything (through managed breathing etc..) - this article explains it very well:
http://www.wombecology.com/fetusejection.html
When all of the above is respected then oxytocin will flow freely and a small amount of adrenaline release (the only time we want it in birth!) will facilitate the spontaneous opening of the birth path, the relaxation of the perineum and the baby will be born quickly and easily, over an intact perineum without a great deal of warning (especially not "an urge to push"). I've experienced this twice now, both of my babies (both very large) were born without any assistance from myself (short of me being very very relaxed, I didn't practice any special breathing), without any urge to push and without any tears to my perineum (birth stories on here:
http://www.birthfriendly.co.uk/about.htm (you have to click for one).
The main aim of HypnoBirthing in my opinion is to ensure that the FER happens and is not inhibited, certainly by keeping women free of fear, relaxed and not stimulating their neo-cortex, plus respecting the birthing environment (dim light, warmth, nobody fussing over her - homebirth is perfect for this) - and it does this very well. Sometimes, however the focuss on J breathing springs the neo-cortex into life - thus inhibiting the FER, so I like to try and get my mums to experience an FER if at all possible and if it doesn't happen for whatever reason, then to move onto J-breathing.
J-breathing is very effective if it's done properly, but I think it's something that is quite often either mis-understood or just not practiced for long enough. I like comparing it to a squeezy tomatoe ketchup bottle. If you give it a shake, a hard squeeze etc..what happens? nothing, you get tired and agitated, but no ketchup. If you just wait for the ketchup to run down and collect around the opening and then give it a little nudge right at the end it comes out easily and you don't get tired and agitated. J-Breathing is much the same, the base of the J when you turn it gives that little nudge I find. The best time to practice is when you're sitting on the loo doing a poo - every day! for a couple of reasons, it's the closest feeling to a baby coming out of you, you'll remember to practice every day and lastly because when we are on the loo we are conditioned into relaxing our pelvic floor and "letting go" - so utilise that and practice there. It's particularly great if you're constipated, try "forced pushing" if you're constipated and then try J-breathing and giving it a little nudge and see which one makes the poo appear quicker (and with no pain)

.
It might be worth you going back to your practitioner for a refresher session, or asking if you can sit in on the fourth class to go over J-Breathing again.
Edited to add I've just read you self -taught for your last baby, this really is the benefit of classes, the book is a great introduction, but you *really* do benefit from having somebody to guide you and show you how to use the techniques (as well as extra hypnosis in class and teaching your birth partner so they can help you on the day) - I've done both, self taught/read the book/listened to the CD and I've been to classes - there was no comparison in the births.
There have been many more practitioners trained in Scotland since your last post. Do look one up, it would be of great benefit to you if you really want to experience a HypnoBirth.
Sarah