Help transitioning to crib

Does anyone have any tips for transitioning a 4 month old from their rock n play into their crib for sleeping? I never want to do it because I don’t want to forfeit the nice RNP sleep I’m getting but I know the longer I wait the harder it’s going to be. And I do also know they aren’t meant for overnight sleep. For the record, my pediatrician suggested it for his reflux. I’ve tried laying him in there for naps and he wakes up instantly and cries and cries.