The younger the specimens the highest survival rate. Adult specimens, for some reason, are more vulnerable to the stress imposed by shipping.
I guess the breather bag would work but I figure that if you manage to get as much water and compressed air into a bag to which you previously added some java moss, water from their tank, and the shrimps, you are ready to send them over.
There is a "thermal device" that keeps the package warm during transit (it's like a pad that looks like those used to absorb humidity but bigger). i have no idea how it's called but UPS/FedEx should know.
For detailed info on how another person did this check this 2008 thread in AquariaCentral:
http://www.aquariacentral.com/forums...d.php?t=140519
Pepetj
Santo Domingo