Frankly speaking, I tend to doubt anything labeled as "simplified". It's like telling a lie. Nothing worth doing can be done in a simple way. That is what I believe in. Yet, anything worth doing also needs to be grasped conceptually by any rational human being with an average IQ. That, incidentally, is also what I believe. So, what do I mean by "Tai-chi Nei Gung - simplified"? Let me explain.
Recently I saw a little book by a master of Chen style tai-chi called Sun GouXi (孫囯玺), who specializes in training students to take part in SanDa competitions and with good results (SanDa 散打 is Chinese style MMA, with point-focus rather than KO). So, he does not belong to "soft-only" tai-chi type. The book is called "100 tai-chi ways to defend against kicks", and his teachings used SanDa as the platform. Like most martial art books published in Mainland China in recent years, the author tried to include as much as possible in his book - probably bad for organization but definitively good for inquisitive readers!
There is a good section of tai-chi Nei Gung there. The 101 of which is simple:
Lie down (in bed) facing up and with arms at both sides. Breath in using reverse abdominal breathing (please check up my Breathing Page if you don't know how), and at the same time, close your fists. Then breath out and open your fists again.
As I said, the concept is simple. The only prerequisite (now that is according to me rather than to the author) for a successful training in the above Nei Gung practice is that one needs to be trained in Zhan Zhuang (standing meditation), through which one's muscles will be "connected together by chi" or "muscles-as-one" (肌肉如一). After one has been conditioned by Zhan Zhuang training, when one does the above exercise, a seemingly "soft" movement of one's fingers (in forming the fist) can activate the muscles groups of one's upper body to contract in succession. This kind of muscle contraction is the gist of what Nei Gung is all about. Corollary: without a proper foundation, closing one's fingers to form a fist can only activate muscles at one's hands (or at best together with one's forearms).
Through the above practice, one's muscular system will be strengthened together as a whole. The breathing acts both as a facilitator as well as a way to strengthen one's Ren Mai (任脈) in the process. The reason for lying down is to facilitate reverse abdominal breathing.
Yes, the concept is as simple as ABC!