The work of a witness is complicated, and it is better to be a professional in international trade and an experienced person, because it involves a wide range, and you can't learn it all at once in any training.
There are several kinds of documentaries, which can be simply divided into: documentaries of factories. Commodity sales of trading companies are divided into domestic commodity sales and foreign trade commodity sales. Generally, the merchandiser doesn't take orders, but only takes orders (that is, the superior will give the orders to you), so there won't be the problem that you said "some people can't receive orders for a year or two".
It is easier for trading companies to execute orders than factories. If it is a foreign trade document, there are requirements for foreign languages.
Generally speaking, the work of commodity sales is very complicated and its status is not very high, but you can learn a lot about this industry. If you are interested in this industry and are willing to do it for a long time, you can try it.
Customs declarers and inspectors must hold customs declarers' certificates and customs declarers' certificates. The inspection certificate is relatively easy to get because of its low gold content. Relatively speaking, it is not easy to find a job. It's very difficult to pass the customs broker's certificate. It is said that only 100% passed, but one of my classmates passed both exams, but I haven't found a job yet.