Of course, I’ve no real experience here except that I did similar research earlier this year. Still planning my run for the border, but for now my order with Mark’s (Thanks again, @Eric) is holding me over. What I was at least told was that a paper rx from a US doctor would be handy. The pharmacists there do the prescribing on site. I’m not real convinced that the paper script is essential to tell the truth, and it seemed like this might vary from individual pharmacist to pharmacist. When pressed on the phone about this, the two with whom I spoke seemed to say it was a matter of peace of mind for them in dosage rather than an essential, but I never confirmed this in person.
Eager to hear what those with actual experience might say.