No need to drain batteries at all.
No need for lipo bags.
Drone itself can go cabin or checked bag.
Almost all airlines state you can check bag your drone with one battery fitted in it.
Other batteries must go cabin.
Batteries must have terminals protected from shorting.
Always pays to check the particular airline policy.
It’s usually as easy as googling the name of your airline and drone policy.
Some now had specific policies, like Emirates.
They won’t allow a drone in carry on.
An example search . . . Emirates airline drone policy
Just a few results down . . .
Emirates maintains a strict dangerous goods policy. It’s important to know what items and substances are forbidden or restricted before you fly.
www.emirates.com
They are about the only airline with this policy though.
Every one I’ve been on domestically or internationally allow full kit in cabin.