Iron Skills Conditioning
Conditioning the body to be hard as iron is not an easy task, and it won't happen over night. It requires determination and consistency in your training.
In old times, fighting was never for sport. It was serious, and failure meant death. Because of this, the body had to be ready to take incredible amounts of damage and still go on. Various systems of martial arts developed training methods that could accomplish this.
Most of the original methods for cultivating a hard and powerful body were not the best choice for someone who wanted to also remain healthy. Nonetheless, they kept people alive, and when they became brittle as a result, there were younger warriors to replace them.

As urgency began to fade, it was replaced with logic. Why condition a hard body only to become brittle anyway? And so the harder conditioning was replaced with softer methods. The iron palm training is a good example of this. Slow and careful replaced fast and reckless. Instead of striking solid objects, they began to strike beans.
Consider it like this. When a stone is formed through heavy pressure under the surface of the earth it becomes a metamorphic rock, with tends to be brittle and jagged. A rock formed by water, however, will be smooth, yet very hard to break. In this same way, we use a gentler, more flowing method for cultivating a body that cannot be so easily broken.

In the image above, I was 19-years-old, performing a special internal training in the snow, wearing only damp shorts. Developing this skill begins on the internal level with a practice known to the Tibetan Llamas as Gtumo. At this time I would take ice cold showers and meditate in the snow until I felt more warm and comfortable. It's not about braving the cold. It's about conquering it.
Iron Skills doesn't only refer to handling getting hit. It is an overall training system for developing an immunity to disease, extreme temperature, and any other issue which mankind is typically sensitive to. Not just to ignore it, but to conquer it.
My own training in such methods began with Ninjutsu, and then the Hojo Undo of Goju-Ryu, and then later the Iron Skills of Shaolin training. I also learned methods from Muay Thai and other systems. At the age of 12, a kid was about to hit another boy with a bat. I knocked him away before he could swing it, so he swung at me. With a forearm block, I stopped the bat. The fact that it didn't harm me scared this kid, and he ran. This was the result of training since I was 5, getting hit with metal wires as part of my training (I'll explain that training later).
When many people think of this kind of training they imagine people thrusting their hands into burning coals and getting beat with sticks. First of all, the burning coals concept is a myth that began as the result of people using fire to keep gravel from freezing while they trained.
The true Iron Skills conditioning is not just a hard practice (striking the body). It includes many soft methods, such as the isometric conditioning methods and internal training, found in Qigong. So, befre you enter into the hard methods, begin with a daily Qigong routine, and then begin with the most basic training methods. At first, the only hitting of the body should be from your own hand, to stimulate the nervous system. Then you can employ the use of a long bag of beans. No sticks.
Dit Da Jow
Any instruction regarding the practice of iron skills conditioning should begin with an explination on Dit Da Jow (falling hitting wine), which was first used by the Shaolin monks in their iron skills training, and has evolved over the centuries. However, Dit Da Jow is not only useful for conditioning the body, it is also quite efficient in healing bruises, sprains, soreness, and several other ailments.
Though there are plenty of online sources for purchasing a ready-made bottle of Dit Da Jow, I recommend making your own. Manufactured Jow is not of very good quality, and even the smell of it isn't right. A propperly prepared jar of Dit Da Jow will smell of the aroma of many herbs, while those purchased from catalogs smell of rubbing alcohol.
Making your own jar of this liniment can be a bit tricky, as the propper herbs tend to be hard to find (if you're using a traditional recipe, that is). However, thanks to the internet, you can find Dit Da Jow kits to get you started. The next issue is knowing how to prepare each herb. Fortunately, there are some sources which will prepare it before putting it into the kit.
For more information regarding Dit Da Jow, and for ordering a kit, click this link.
After allowing a gallow jar of Dit Da Jow to sit for a long time, I pour some into a smaller jar to take to training and leave it there. The label is just paper glued to the jar, with the logo of the Kouryou Kai (a private Martial Arts organization).
Always store your Jow in a glass bottle, in a cool place. NEVER use plastic!

Hard vs. Soft Conditioning
In the Iron Skills training, the conditioning methods can be divided into two types. Hard conditioning is what likely enters your mind first. Hard conditioning is the beating of the body to force it to heal stronger. If not implemented correctly, it can lead to life-long injuries. Soft conditioning is all other forms of conditioning. The soft methods can be divided into physical conditioning and internal training.