How difficult is it to ship to Canada and other places out of the United States? (internationally )

In most cases , when shipping in the USA I use 8 1/2 x 11 bubble mailers . The weight is usually between 4 to 7 ounces.

Do most of you use Global priority envelopes ?

Has anyone had "headaches" shipping out of the states ?

Is Paypal the best way to go on payments from out of the USA?

I did find the pricing on Global priority on the USPS.com site .