I have never shipped to Belgium but I have shipped to 11 countries including Russia, Austria, Switzerland, England, France, Germany, Spain, Malta, Australia, New Zealand, Canada, and Singapore. You can accept your payment via Paypal just like any other payment. If you don't have paypal, PM me and I will accept the payment for you and transfer the money with no fees.
As for shipping...USPS is the cheapest and most preferred for intenrational orders by the receiver. DO NOT use the Small Flat Rate Box, however. IT IS NOT TRACKABLE. I know this from personal experience learned the hard way. You can track it until it leaves the US but after that, you are on your own.
I replaced a $400 order of Cactus Blanks because it never made it to the receiver. I tried tracking it and hit a wall. I called the USPS and gave them the tracking number. They said they could not do anything for me but if I had used the medium flat rate box or the express mail, they could help.
Then, a few month later, I shipped $1,000 worth of blanks to an Austrian customer. Due to the size of the order, I used a medium flat rate box. After a month, my customer contacted me and said they had not received it. I called USPS and they tracked it and said it was stuck in customs in Austria and that they would do an inquiry. It got delivered the next day!
Hope that helps some.