Replying to [Englishman in Shenzhen]:
Yes, I agree with Englishman in Shenzhen, in most cases an agent (or medium) is necessary to expedite the trading process as they serve as "man on the ground" when the purchaser does not have the time or resources to do all the legwork/documentations themselves. I myself have been employed in a steel trading company for 17 years already, and we represent major mills around the world as agents.
In the trading/indenting business, a good solid reputation is a must. More especially in the steel industry, as buyers do not easily trust mills/manufacturers to deal directly with them. They rely on agents to ensure that the specification they require will be supplied by mill. And in case of any dispute, they will chase after the local agent who they have a working relationship with, rather than the mill who is abroad.
Just be sure that the agent you are dealing with is well-informed and has a solid reputation. Because dealing with a technically knowledgeable, honest and reputable agent is invaluable, and makes your job already half-done!