The place I've had the best luck in actually
trading with cast members was Animal Kingdom.
The best Cast Members to look at for trading are, in order of preference:
1.) Managers. If you see someone wearing business attire, holding a pick-up-stick, and wearing a lanyard, I bet they will have at least 1 pin you like. They are hard to spot though, obviously.
2.) Character attendants. Character attendants generally see a very high volume of trading, because they see so many guests, and since the guests are just waiting on line to see the character, they will usually take the opportunity to trade. However, having spent time with character attendants and knowing their gripes with pin trading, there are some "etiquitte" rules I generally follow when I want to trade with them.
a.) If their line is really nuts, ask them if you can look at their pins just before they go backstage with their character. You can probably spot where the character will be exiting, so I'd stand near the exit, but not in the way of any cast members.
b.) If their line isn't too long, just wait in it. Then you get to see the character too
c.) I am always extra polite to attendants, and make sure I am not interrupting them, because they have many duties, and one of them is safety for the guests and for the characters they are with. Showing respect for those duties is the most important thing you can do for them.
And never be embarrassed to trade, even if you're a grown up. As long as you are polite and follow the rules, it is never a problem. I've heard stories (and MET) what my sister and I call "Crazy Pin People" who are ALL about pins, and ignore everything else just to get the pin they want. This includes running down other guests and CMs with an electric scooter.