I think there is a luck factor as to how easy the process is

Good evening
We just went through the all permanent residency’s process and completed yesterday

Our consulate appointment took place late august in Montreal .

In fact they didn’t have any available appointment until late November but our office is just a 10mn walk from the Consulate, and I told so to the clerk. The next day (a Thursday I think) he wrote me as there was an opening the following Monday after someone cancelled, so we were quite lucky on this first phase!!!
But we had just a day to get all the paperwork, which was a little tight. We only receive electronic bank statements, and so we had to print them, then have them certified by our bank branch, which is 50 miles away.

The appointment on the next Monday went fine, the Mexican clerk was really helpful.

At the end he asked us when we were planning entering Mexico, we answered early November, and he told us that we should have our permanent residency card before Christmas… According to some information I found online (INM web site I think), the usual delay is 4to 6 weeks apparently.
But some applicants (as in this post) stated that everything was completed on a single day, or just a little more, but not 4 to 6 weeks.

So a couple of weeks ago, a week before flying into Zihua, I decided to call INM and get an appointment (phone numbers below), appointment which was yesterday.
They didn’t have any availability before.
I guess that November is probably a really busy time with expats flying in…
Also the Otis mess might worsen the situation as there were people from Acapulco waiting with us, not sure if it’s just incidental?
It took us 3 hours yesterday, we lost almost an hour as our credit card would not go through (works as a charm in most places as Mega, Sam’s and number of restaurants, but not INM , so I had to get back home to get a secondary credit card which did pass hopefully!).

So only thing now will be to go through the « small office » at the airport when leaving the country.

Good luck on your next phases to come!
https://www.inm.gob.mx/gobmx/word/index.php/guerrero/

INM – Representación Local Zihuatanejo
Calle Heroico Colegio Militar No. 115, Col. Centro, C.P. 40880, Zihuatanejo, Guerrero.
Teléfonos: (755) 554 1447, (755) 554 2795
Horario de Atención al Público: Lunes a Viernes de 09:00 – 15:00 horas.

The IMN office is slammed right now. We called and called, no answer. We flew in on Tuesday and went there yesterday, waited two hours to talk to someone. They wanted to make an appointment for us on Nov. 22nd. Said sorry, that is the day we are leaving to go back. So they put us on for Monday. Will see how that goes.