Hello Bruno!

One finger per fret wouldn't apply to this. Also, I'd be suspicious of this originally being done on one string. It's inefficient, and not sure why the guitarist would have done it. On the studio recording I hear some additional slides up to the lower notes that lead me to believe it wasn't on one string.

I would change it to 5 and 7 on G string and 5, 6, 8 on B string.

If you really needed to keep it on one string, you'd switch between two different overall hand positions. Here's how I would break it up.

First hand position: frets 5 and 7 with index and ring.

Second hand position: frets 9, 10, and 12 with ring, then also sliding from 7-9 with index.

It's a hassle, and it's a lot of ring finger. It can be done, it's just not natural.

BUT: in this live video, he plays it all with one finger (middle):

https://www.youtube.com/watch?v=-lvM30oTm3Y

That's a ton of sliding, very easy to miss the notes (he misses a lot in that video), and you *could* think of it as a good sliding workout.

-Carl.