I think the main reason why dogs can sniff out pot that is well packaged is because the people who did the packing probably had minute bits of resin all over their hands and spread it all over the packaging. This makes it too easy for the cur to find his or her treat. This idea was alluded to in the information above, but I think that it is the major problem with transporting weed and this cannot be over emphasized. So when packaging weed for transport, have the person with dirty hands carefully put the weed in the first package, and another person who is clean finish the job. Preferably wearing medical type gloves.