Extra Armies for Regions in Team Games

Can someone explain how you get extra armies for entire regions when playing team games? Does a single player need to hold the entire region, or can multiple members of the same team hold the region and get the extra armies? If the former is true, then is there a way of transferring territories you control to your teammates so they can gain an entire region (short of having them attack you)? When do you receive the bonus armies? Thanks!

Does a single player need to hold the entire region? Yes.

is there a way of transferring territories you control to your teammates so they can gain an entire region (short of having them attack you)? They can attack you and vice versa, you can transfer your troops to him and vice versa, it's the same as regrouping troops 

When do you receive the bonus armies? The next turn if you manage to hold the region.

How do you transfer troops to other players? Can you simply take one of your own territories and change it to a fellow team member's color? How is that accomplished?

If you can't change your own territories to another team member's, then is having them attack you the only way to give them the territory? Is there any way to surrender it to them without running the risk of them losing armies from me having high defense rolls? Can I simply walk off the territory and leave it vacant?

Just reinforce troops at the end of your turn to your team mates territory.

I understand how to move troops from my territories into my teammate's territories, but I am wondering if there is a way to actually hand over a territory itself to a teammate. I'd rather not have to have them just attack me, especially if I start rolling 6's. Is there a way to accomplish this?

No there isn't.

You have to attack the territory in order to take it over.

Are there any good strategies to do this effectively and with the least amount of armies lost?

communication with your partner is key. in this scenario you would ask your partner to move the bulk amount during his tactical move phase at the end of his turn

The best way to do it is for your team mate to fortify your troops at the end of their turn, leaving theirs with 1 troop, so you have plenty to kill the 1 troop and it has minimal losses with great rewards.
As Hoodlum said though, make sure you discuss your tactics in the Team Chat.