Little by little

So my son is doing better and better with me putting him down at night without rocking him, I have just been laying him down and rubbing his head for about 5 minutes and he’s out. Now we have to make progress on naps. I just feel bad for my mom bc I got him used to napping in arms so she has to hold him for his naps during the day while I’m at work. If she puts him down he’s up about 30minutes later and then gets fussy faster bc he needs more sleep. Like a never ending cycle. Does the Ferber method work for naps too? Or can it be applied even if we don’t do it for bedtime?