To defeat boses such as ,articuno , moltres and Rayquaza, people have been saying that you need to be high levels you don't i was level 32 when i did it. A good move that you can use alot and a good rescue team. I used "BULLET SEED" it takes of about 169 off at a time depending what level you are but if you havn't got it dont spend ages looking for it!

Note: It won't work as well if your not a grass pok'emon.