I've been pondering what I know of the new trading system (not enough, so some of this is speculation), and have come to the following conclusions.
The best way to trade legendary pokemon with poor IVs is to trade them with someone who lives over 100 km from you (or caught the legendary 100 km from you), and someone that you are best friends with (to reduce the stardust cost). Of course, you have to meet with them in person to make the trade.
Benefits - reroll IVs for legendary pokemon, which require some investment to get, trade for pokemon you want and trade away ones you have plenty of, get 3 rare candy for the pokemon you trade away (instead of the one you can get for donating it to the professor, or two during a double candy event), and add to your trades made and distance traded medals. The distance is important because for 40,000 stardust, I'd much rather get the guaranteed three candy instead of just one.
Disadvantages - cost of 40,000 dust to make the trade (be sure to be best friends first, or it gets worse), limit of one trade per day because it's a special trade.
What this means to me is that it is important to become friends with people far away (over 100 km) that you will see on a regular basis. Friendship with some random trainer on another continent won't do you much good if you're never within 100 m of them to trade.
So I strongly urge all of you to identify other trainers you know from other cities that you will see in the future, and work towards being best friends with them. In three months or so, when you see them next, you can trade legendaries, getting rid of your worst IV ones, gaining 3 candy, and possibly getting a good IV legendary in the exchange. Worst case scenario is you get a bad IV one, and then give that to the professor (since it is untradeable, AFAIK) to get another candy.
Naturally, we don't have all of the information above verified, but this seems to me to be the optimal use of this kind of trading, given what we know about the rules. If the rules are different, some of this may change. And there are other tricks to pull off, like a pair of trainers from the same place traveling, trading one from home for one from the trip, and then vice versa. But in any event, figure out who your distant trading partners are and work towards best friend status with them. That's what we need to do now to make this happen later.
Thoughts?
