shipping companies vary, youll hear it from both sides, just get quotes from all and use the cheapest overnight method
ive had great success with ups, usps (both express and priority) and very bad results with fedex, my personal experience
location of the buyer has a huge impact on the carrier though
also, what coral you ship has a factor in the shipping method too
if theyre within the same state, most of the time you can get away with ground shipping
i find that triple bagging is overrated, i only double bag unless the buyer insists
i know everyone swears by it but if the inside of the box is packed/bagged well, you really wont have a problem
styro lined box is great but a styro box is better but much more expensive
i used to buy styrofoam sheets from homedepot for $10 which made a lot of boxes
if you do styrolined boxes, remember to tape up the edges because unless your cuts are perfectly squared, it really isnt doing much
i like to bag up all the bags into 1 big bag just as a precaution, so if you count the big bag then i guess you can say its "triple bagged"
good luck