My friend and I still both need the gold dragon medal (Dragon Tamer). Assuming we have enough stardust, can we just trade Dratini back and forth all day to increase our count and get the gold?
Yes, traded Pokémon will count towards the medals. I tested this with a friend and the count for the medals increased after the trade.
However, you cannot trade the Dratini back and forth in this manner. Once a Pokémon has been traded, it cannot be traded again.
Pokémon that have previously been traded once before cannot be traded.