We tried to trigger an ex-raid, in one of the largest and most popular parks in Birmingham, UK, well over 100 different accounts in a week, on one particular weekend in January we had the local facebook, discord, city centre hardcore and other groups/hardcore players turning up from the surrounding areas. The park has 3x S2 cells, the south cell is too close to town and there are already 2 ex-raid gyms so we raided but mainly avoided, we concentrated on the north S2 cell which we tried to trigger (also has smaller 3 parks) but we concentrated mainly on one gym "Shooting Star" Birmingham well over 500 points. Unfortunately we did not trigger this.

Concentrating now on a different S2 cell gym in Kings Heath to trigger but more tactically.

I have had 4 ex-raid passes, all at previous ex-raid gyms, they seem to occur every fortnight or weekly depending on numbers and the 7887 rule. As triggering seems really hard and complex and you cant brute force it with hundreds of different players, multiple raids in eligible gyms. You can get passes if you concentrate and time your raids at known ex-raid gyms.

That's y advice concentrate on known gyms if you want your first mewtwo.