Well its well spoted on country records but i will probably make an arse of my self right now giving you example in Metallica - My friend of misery pre solo part.
I'll try to find country example i just want to add that i heard a sample of swell sound years ago when the first POD launched.
Might be or somewhere close maybe its a combination of dunlop slides and technique but that has something to do with POD's sound as the sound was really nice.