I still do it old school style. I have the classic North American Field Guide. I have the modern publication and my dad's 1960's version. There's been a few updates on the range of the birds and the classifications. https://www.amazon.com/Birds-North-America-Identification-Martins/dp/1582380902

I also have another book with photos that focuses on my particular area. This information isn't as in-depth, but it's great for scanning when I have no clue what I'm looking at.

I also rely a lot on the Audubon website and Wikipedia.

While using field guides may feel more difficult than using an app, after time you tend to get really good at using the guides. I feel like when I use apps, it's more the phone doing the birding rather than me. I don't retain a lot of the knowledge with the apps. Using the books implants the information in my head better because I have to locate and identify the details of the birds.