Thanks for all of this info!
Here are some spoilers regarding filming of the finale (based on casting calls and social media postings).
Filming dates: April 26-May 24.
May 6: Filming in Cambridge (Moss and Dowd were spotted)
May 7: Scene with Stenographer filmed (source: ML Talent Agency FB page)
On this same day, someone tweeted this to Alexis Bledel. This person is a freelance photographer/videographer in the Niagara area. Not sure if Alexis was filming though.
https://twitter.com/fireman607/status/1125943998944821249
May 13/14-17: filming at airport in Waterloo area. A lot of this seemed to be during the overnight hours. Several tweets mentioned this:
https://twitter.com/SheilaBauman/status/1128800949873647622
https://twitter.com/SW_ON_TRAFFIC/status/1129473374672097281
-I believe child actors may have been filming at the airport, based on the casting calls from the Toronto Talent Agency FB page. According to a post, the actors needed to be there at least one night between May 14-16.
May 21: Filming in Galt, Ontario:
May 23: Amanda's last day, kids filming
May 24: Last day of filming (Moss on set).
I think the only confirmed cast members to appear in the finale were Elisabeth, Amanda, Ann, and I think Madeline Brewer. Also
Two interesting characters from the finale: escapee econowjoman, escapee Martha.
There are three stunt doubles, including Melissa Kelly, who also worked as a stunt double on the season 2 finale. I'm guessing she would likely be Alexis Bledel's stuntwoman (I'm assuming she was her stunt double during Lydia's stabbing in the season 2 finale)
Remainder of the cast:
Yvonne Strahovski was in NYC in late April, and was seen by a fan at LAX on May 8. She wasn't at the wrap party, so I have no idea if she was in Toronto at all for the finale.
No idea if Joseph Fiennes, Max Minghella, Samira Wiley, or OT Fagbenle were around during the finale.
Ever Carradine is not in the finale (her finale appearance is episode 12).