I recently mailed two packages to Canada.
I printed the postage and customs forms from my Stamps.com online account. Both sent as large envelopes, so i only needed the simple customs form.
I took one to the Post Office. The other I handed to my mail carrier on the 24th.
I don't know whether he scanned it in his truck or once he got it back to the PO.
I just went online and input the tracking number of the package i handed over to the carrier. I know it left Jacksonville, FL (which is two hours south of here) on the 24th, headed for Canada. there's no additional information (yet?).