Recently I heard much about the Golden Turtle, or Tortoise, around me (24 styles tai-chi nei gung Golden Turtle stance). Some of my acquaintances complained that doing the Golden Turtle hurt rather than cure (well, they didn't learn from me). And one even say something like "How come your Indonesian maid enjoy doing the stance?" As usual, I smile in response. What can I say? People just jumped into the stance having the no-pain-no-gain attitude without knowing what they actually want to achieve, or without the patience to feel his way through the stance, or just like learning any new fad and drop it a few minutes later saying it's no good to him? The bottom line is, every practitioner finds his own way, with the Turtle or without the Turtle.
For anyone who has a few months' experience in doing basic Embracing zhan zhuang (correctly and having felt his way and learned!) can start doing the Turtle. Sometimes I would joke to my students: I don't trust the Turtle, it will bite back! What I mean is, one has to ease oneself into the stance. There are infinite number of ways to ease it in. In the old days when I learned the stance, it was a verbal tradition for the easing in, and with lots of variations, that depended on the student as well as on the teacher, I mean even within a teacher's repertoire there were variations to the basic way. And I observed (and I was an avid observer), I asked why to myself, and I figured it out and I learned, in addition to what was being taught directly to me.
Embracing is my first easing in stance. And "Junior Turtle" (i.e. with forward stretch and no full bending/squatting) is my second easing in stance. They are compulsory in my teaching repertoire, by the way, because I don't believe in no-pain-no-gain in chi-kung, it has to be enjoyable!
Now we do the Turtle proper, with a twist, like lowering a heavy ball (i.e. YiChuan style visualization). Objective: not to put too much burden on one's back. If you've a strong back, they can do away with it, but I always insist on my students doing it.
After the Turtle proper, I will do a stretch front stance, in addition to the usual stretch back (between the legs) stance. Chi generated from Turtle proper can spread more evenly to the whole of the body.
As for breathing, do normal breathing, unless you know reverse abdominal breathing, then do it, it is the ONLY way to move chi to your extremities (like finger nails). For the most advanced student, hold your arms close (touching) your rib cage, but leave it out if you feel uncomfortable, it might do harm.
Do it properly, the Turtle will love you and you will love it. Otherwise, you might have to pay a price for its vengeance, don't say I didn't warn you before hand!