Swing feel isn't a closely guarded secret among jazz musicians - it just isn't quick to explain. There's a sliding scale of the ratio between the first and second eighth note, where at slow tempos it's 2:1, and at fast tempos it's 1:1. The exact ratio at a given tempo is something that's passed down aurally. There's also a harder articulation on the second eighth note. There are other nuances too, but those are the most important ones.