People that try to cover the smell of weed from dogs by using coffee and other substances would be out of luck if dog trained to sniff marijuana was present. Masking substances just won't work on a properly trained dog. The sense of smell of a dog is so specific, they will just say, "hey, I smell coffee, I smell plastic, hey there's marijuana!" (they alert because they think it's their favorite toy/ball. That's how their trained). Drug dogs have found weed inside sealed plastic, inside a full gas tank. If the odor can permeate through the gasoline and the outside of the gas tank and, don't think that coffee or anything else will work.
When you put weed in a bag, then touch the outside of the bag, you will transfer some microscopic material, with the odor to the outside of the bag.
After you put it in a bag, put on some latex gloves and then drop the bag into an open vacuum pack. Remove the gloves before handling the new outer bag, then seal it. The odor will permeate through the outside of the bag eventually (even glass has microscopic pores that allow odor to permeate through), but it does take some time and the smaller the microscopic holes, like in the vacuum sealed bags (regular baggies are very permeable), the longer it takes.
If you do this just before you leave for the airport, there won't be enough time for the odor to permeate the outer bag and even if they happen to have a marijuana trained dog around (most are trained to smell bomb material) they shouldn't alert. It seems like a lot of work, but if you're really paranoid, it will help.
You can do the same for shipping too. DHL is the current shipper of choice due to their lax security and disorganization.