Yes I have, and the key is making sure you are not blatant. I work for at a Fedex Kinkos so I ship whatever whenever with no problems, especially domestically. Your main problem will be conceling. Your statistic probabilty of interception stands around 20%. Get a mail box at a ups or mail boxes etc, that way you will be slightly insulated.
-If you want, you should get a prepaid fedex international shipping label and a fedex box. the boxes are strong cardboard and you could put whatever between the cardboard seals. If you are sending the fluffy, consider getting a good product and inserting the goods in a least damage possible manner... when you fill out the customs form DECLARE your "food" and dont look like you are doing anything wrong... worse case scenario is its is seized. - remember concel it appropiatly, and you should be good... food products, wax, a touristy item should all work. Fedex ships 7.5 million packages a day, if its in a small letter, whose got the time ? good luck