Hi Jackie, my situation is the opposite - I'm the one who is out of the country and all of my clients are in the States or in Canada.
But, I bill everyone via Paypal, every two weeks.
Large projects,
SEO campaigns, and waiting list placement for either requires a substantial advance deposit, also invoiced via Paypal. The deposit is then applied in full to the final invoice(s).
I think Paypal is available to most countries (there are a few exceptions) so this could work well for you in terms of getting your invoices paid.
I'm not any more particular with invoices for clients based on anything other than the scope of their project.
All invoices, for all clients, are managed, recorded, and provided to the respective client in the same manner.
Not sure how other people manage this - I hope you get the info you need!