Thank you so much!
Thank you very much for this info.
I have a good news as I saw it yesterday. You can get them fast by changing time.
1. Find the right spot (I use game8, it's in Japanese but it has pictures showing which pokemon it has).
2. Get a purple beam by using item. I don't know the English name of that item, just press A... I think it is not a problem for CFW version as you can have as many as you want.
3. Once you get a purple beam, press A and choose raid together (or something). Now you are waiting for others to join (Local Player).
4. Now, press HOME and change time (close get time from internet first). For example, today is 23th so change it to 24th.
5. Go back to game, cancel the waiting. If everything goes fine, the beam is still there but the pokemon inside is a new one.
6. Repeat until Mega shows up.
7. Before your fight, change the time back to normal. (This won't change pokemon inside the raid. It only changes 'in future')
8. Save, backup and raid?
PS. You will lose the daily bonus (shop change etc.) for 24 hours after the time change.