Hi Amy! I fill out my customs forms online. I am new to this, and so far I've sent about 15 or so packages. I have no idea if they have reached their destination or not- so hard to send on faith, since every PO clerk has a different story as far as how to send. The one thing I do have to say, if you do your forms on-line, stock up heavily on black printer ink. I used a whole cartridge on those 15 or so packages.
One thing I'd like to know- the clerks at the PO tell me the packages will reach their US destination in 2-3 days when sent priority mail. I called the big 800 number when I couldn't track a package, and the rep on the phone said that is not true. She said military mail is different, and usually takes about 10-14 days to reach the APO/AE site in the States. If that is the case, why are we paying for priority mail?
Back to subject, I do like the convenience of using the online forms. I weigh the package first, print out a click and ship label (postage paid on-line), then fill out the customs forms, including 'total postage'. Then I schedule a pick-up from my carrier (free with priority mail), completely avoiding the hastle of going to the PO. Interesting enough, it's the packages picked up by my carrier that I HAVE been able to track, and the ones I took to the PO I have NOT been able to track. Schezz!
I had to order the customs envelopes on-line, PS Form 2976E. I only wish I could tell you my packages made it to the destination, but I have no idea! Good luck!