Golden Bridge (see pic) as taught by my teacher, Sifu Wong Kiew Kit, is a form of Zhan Zhuang or stance training. Various forms or postures of Zhan Zhuang develop energy in different ways. Specifically, Golden Bridge develops a pearl of energy at dantian and a sheath of protective energy around the arms.
In my experience, practicing Golden Bridge did exactly what Sifu Wong said it would -- make my sparring partners complain that my arms feel like wood. It also eliminated all of the the forearm bruises I used to get during sparring. It is significant to note that I did no external conditioning, but only Golden Bridge.
The methods for this exercise are detailed in Sifu's books, but it's best to learn from an instructor (unless you have prior experience in Zhan Zhuang). Also, adding weights is definitely not part of the method in our school.
Hope that helps.
