I send "care packages" fairly regularly and never had any problems. It's typically a 1/4 oz or less, maybe up to 1/2 oz. I package in multiple layers of plastic bags and Saran wrap, wiping down the outside of each layer with alcohol to make sure there's no residue from my hands (which I clean with alcohol after I seal the first layer). Never had an obvious smell outside the package, although I'm sure a dog would detect it. For 1/4 oz or less, I sandwich between 2 CDs/DVDs, tape it together securely, and slide it into a small, padded envelope. For larger amounts, I've taken apart a VHS tape, stuffed it in there, and put the tape case back together. I figure either way, it would look pretty normal in an X-ray. I also don't think they take the time to check envelopes too closely, as they really couldn't hold any significant amount. And I use a fake (not mine), but real (someone's), return address. Works for me.