I too used Gina Ford on both of mine but adapted it to suit my children.
I only stuck to the nap and feeding times I didn’t do all the dark room stuff if we were out they just slept in the pushchair.
the main thing for me was the dream feed at around 10pm. I noticed lots of babies would go to bed at 7pm and last until 2am then go back down after a feed, so the dream feed “shifted” the long stretch for us which meant much better quality sleep for all.
i also adapted the schedule to suit. My daughter (first child) the nap times and routine suited her perfectly.
My son never napped much, he preferred to just have one longer nap in the middle of the day and go to bed earlier at night.
if they had a growth spurt I’d feed them more of course or earlier.
daughter slept through from 6 and a half weeks (after dream feed) and son from 9 weeks.
it saved my sanity.
I don’t know why it gets such bad press.
carrying my babies in slings, co sleeping, no routine is right for some babies and mums and that’s fine by me. I don’t judge that so it really upsets me when people are bothered about the way I preferred routine. We’re all individual.