So far I never sent an instrument out of China, but I had two guitars sent from overseas to China. One was send from the U.S. to China via USPS / China Post and the other one from Germany via DHL / China Post.
Both instruments arrived here in perfect condition. They were packed in the sturdy Gig Bag or in the Hard Case inside a simple carton box, which, however, was filled with material to prevent the cases from moving inside the carton box. I wonder if it would work the other way around as well. Shipping time was in both cases around three weeks. Both shipments came by air with low priority, that's why it took so long. Definetly refrain from sending it as checked luggage. This way I ruined my 12-string guitar, although it was packed in a hard shell case, designed for this purpose.