I often specifically search for songs that use a technique that I want to learn and use this song to learn and practice the technique. I asked my teacher to teach me altered versions of the song Silent Night to practice double and triple stops and arpeggo and I learned a violin version of the Pulp Fiction theme song to learn and practice satullé a few months ago. With only the thechnique alone I couldn’t motivate myself to practice. I don’t just head from song to song though, I usually practice the songs and techniques pretty long before I start the next thing, but mostly because I am too lazy to learn new songs.
The songs are practically the engine of my practice.
I think the best thing is to learn songs, analyze it’s structure and write it down in a way that is easily readable. Scales, notes, rhytm, arpeggos… I should probably start doing this.