How to effectively export Plantation surplus?

I am overproducing plantation goods and need to know exactly what is required to sell them off.

• Trade Centers: Do I need a Trade Center to sell these, and how exactly can I increase my sales volume?
• Treaty Ports: If I take a Treaty Port from another country, does it force them to buy my products? Do I also need to build a Trade Center in that region as well?
• Monopolization: Should I be trying to monopolize the foreign industry?