Careful with Iron fist, Iron palm.
WKK's methods are OK, but if you truly want an "Iron fist" It takes alot more than that, and is hardly necessar nowdays (do we need to kill or punch through walls).
Practice basic stances. You should be able to find them in many gong fu books. The "cat" stance as many call them (or empty, Xu Bu), the horse stance (ma bu), gong bu (or bow-arrow stance), Pu Bu (lower stance), and Xie Bu (crossed stance). Also try the crane leg stance (leg up, 45 degree up), and hanging leg stance in there for balance and flow purposes. Sit in them at first for a while, and keep back straight abdominal breathing. Then practice moving from one to the other. The stance should stay LEVEL (no bouncing up and down), unless you are jumping from one to a single leg stance (even then its better training to stay level). Don't be stiff, rigid, and slow, flow from one to the other until you can flawlessly transition from on into the other without too much effort, and deliberation.
Wubu quan is a great wushu form with all the basics. I would recommend that, you can find it in alot of the basic wushu vids. Make sure to use full twisting waist power in every punch, make sure to never stiff, relaxed, but never too bent.
Truth comes from the absolute stillness of the mind...