I've had one transaction with 4.cn, some years ago, but it was all done by a broker who contacted me with an offer. All I had to do was open an account there and let her run the transaction. It was a great offer, so there was no real downside. It went perfectly, although I was uneasy at relying on someone else so much due to the language barrier. They are a huge and professional marketplace. Here are a few threads you can read to see what others' experiences were with 4.cn:
Oh, and I wanted to ask you to explain what you are calling a "Chinese domain." Is it a CHIP, or a word in Pinyin, or what? Depending on what kind of domain it is, there are likely to be various alternative marketplaces to consider.