For international shipping, freight prepaid is requested according to common rules.
Despite payment can be made after vessel sailing, it must be received before goods arrival at destination port ( i.e, Before shipment released actually )
T/T ( Telegraphic Transfer) is the most used payment method.
For Alibaba overseas buyer, there some appointed countries could also pay via Alibaba.
Money Gram/Western Union is no more accepted by China forwarders due to the bank regulation more strict.
Paypal can only be used to accept small amount under $ 1000.