Happy sleeper method

Hi ladies, just wondering if anyone has tried the Happy Sleeper method of sleep training? We’re on day 5 and my 5 month old is doing really well with bedtime, we do our bedtime routine x 30 mins, put her down in the co-sleeper cot, she cries for 3-4 mins and goes to sleep. This is a massive improvement from where we were a week ago where she hadn’t fallen asleep once since 4 weeks old on her own in a cot, she was always either fed to sleep or rocked/walked/slept in carrier etc. so I highly recommend the book for bedtime. However her naps are so so much harder. She is crying for anything between 10mins to an hour, I’m checking every 5 mins and using soothing phrase like book says but it’s killing me listening to her cry for so long. Has anyone been here and could give a little advice? Happy to hear about other modified methods of Ferber method for naps. Thanks ladies