I know this is really a long way into this thread, but thought this answer might help someone else who is planning on starting to ship regularly (or even ship the occassional fish out). I knew nothing about it before my first time just as everyone, but because of our rural location, shipping was the only answer if I planned on selling fish (and I did plan on doing just that). So I read everything I could, then jumped in.
Step 1: For the 3 days prior to shipping, NO food for the fish (so if I'm shipping on a Monday, I feed on Thursday evening, but starting Friday am, no more food). Then you'll have WAY less ammonia in the water.
Step 2: Starting either the day I start starving (in this example, it would be Friday), or possibly the day after IF (and only if) I've done a partial water change very recently - I'll do a PWC each day up to the day of shipping. So in my case, minimum would be Saturday and Sunday, but if it's been like a week since the last WC, then I'll add Friday as well. Then when I'm ready to ship out - the water is VERY clean.
Step 3: Bag buddies are only intended to last UP TO 7 hours (call them if you doubt it). It's only intended to get the fish "safely" from the fish store to your home. Jungle is quite honest about this - somehow we fish folks have made it out to be more than it's meant to be. So that said, if you use Ship Right (also by Jungle), it will last long enough for even a priority mail shipment. You use only a fraction of a teaspoon for a quart of water.
Step 4: As I am bagging my little wet pets, I use half of their very clean tank water with half new fresh water (with chemicals of course if you have chlorine - we're well water so it's not an issue). I put the Ship Right chemicals in the empty bag, add the tank water, the tap water, then net the fish in last. One big key for success is medical oxygen if you can get it. We have several friends who use oxygen and give us the small tanks when there's not enough in it to do them any good, then when it's empty, we give it back to them for them to refill and get the next "almost empty" tank.
Step 5: When filling the bag with oxygen, squeeze out ALL the room air, insert the tube for the oxygen and fill. Carefully and quickly remove the air tube so you don't loose your wonderful oxygen.
Using these techniques, I've sent MANY 4 day shipments, a few 5 day ones, and even a SIX day shipment (only one so far thankfully). In each case, the fish were fine (the only exception to that was when I shipped some fry that were to small to stand going without food during the delivery time - and I didn't starve them prior either). That Ship Right is a great stress reducing chemical and also allows them to better use the pure oxygen that is in their bag. I use 3 cups of water in my bags and it's between a third and a half of the bag's volume, but because of the chemicals and the pure oxygen, it's still plenty.
Oh, one more tip for you guys - if you don't want to have to pay for styro shipping containers and you don't have fish stores close, contact your local vet offices, pharmacies, and doctor's offices for small boxes (perfect for 1-2 bags). If you need bigger ones, Walmart will usually save them for you if you ask right (make friends with the fish department folks). Maybe it's different in larger cities, but you'll never know till you try.
I hope this will help someone who's just "getting their feet wet" with the shipping scene. Now I will mention that the Ship Right is generally sold in a 9 pound container which would last individuals a lifetime - BUT there's one nice person on aquabid who sells 1 pound containers. I'm only on my second pound even after a lot of shipping. I suppose it would be a good thing if they broke it down even smaller, but it's only like $10 for the pound and it keeps really well. Good luck to all you wonderful caring fish shippers!