Being a musician, there's no way you can do without learning lyrics, without knowing the lyrics, one will definitely be singing the wrong thing, you have to master the lyrics of the song you want to score, and we can do this in our different ways and patterns but the goal remains the same, which is knowing the song well enough.
There are two different and popular methods that can be used while learning the lyrics, so whenever I want to learn, it's either I write it down with my pen on a paper or I browse the lyrics on my phone maybe through music apps, or just Google it and check while I'm listening to the song.
Actually the most stress free is checking the lyrics on the screen, you won't have to disturb yourself to write down the lyrics, because that method can be so tiring and frustrating, especially when the lyrics is enormous, you'll continue writing and writing as if it won't end. This method will be very good to use when one has a music application that can show you the lyrics of the song you're currently listening to, it will be very easy that way. One of the apps I know that has this feature is "Boomplay", it's very effective, there are other music apps as well though.
Another way is by making use of two phones or gadgets, you can browse the lyrics on one phone and listen to the lyrics on the other phone, I do this when I can't find the lyrics on the music app, especially the indigenous songs, you hardly see the lyrics on these apps, and sometimes you won't even see the lyrics online, you have to write out the lyrics on paper, and that's how the second method comes in, writing out the lyrics with pen on a paper. It can be very stressful and annoying to do atimes but when I don't have a choice, that's what I do. For me I don't see this method as the best because of the stress and then I'm a kind of person that's so used to my phone, I prefer doing almost everything on my gadgets lol. So for me, I'll forever prefer learning lyrics on screen rather than using pen and paper.
I'm that kind of person that make use of the pause and play method to learn songs. I score songs line by line, when I listen to how the singer songs a line, I pause the song, try to sing it that same way and then play the next line, I continue in that order till I'm able to get everything, this method has been very helpful, because when I use it, it makes me score the song, sing it almost exactly how the original owner of the song sings it, then I can now add my own flavor if need be.
As a vocalist and instrumentalist, I don't learn the lyrics of a song alone, I also try as much as possible to learn the Rhythm, so it's a kind of double work, learning the lyrics and learning what's being played to the song especially with my musical instrument. I play piano and guitar, although still at amateur level but these are also some of the things I look forward to learning as I'm listening to songs.