I don't think you can. You can set multiple "options" for customers to use, but that's for all international customers and of course everyone will select the cheapest method without me being able to do anything about it. If there is a way to set it by each country, I would love to know how.
I wish ebay set an option that let me accept or decline orders before getting immediate payment. That way I can adjust/change shipping methods based on countries or decline orders if customers have 0 feedback or whatever.
Recently got scammed almost $1k shipping 4 rigids to a proxy somewhere in South El Monte, CA. Japanese customers with stolen cards. I knew it was suspect because they bought the same item, with different accounts, with different names but since I never get scammed by Japanese I shipped everything. Paypal has me covered though since I followed all the guidelines for SP.