Watch the Mrs. Crowe's Blue Waltz online guitar lesson by Adrian Legg from Fingerstyle Revisionist: Adagio Songbook
Let's begin by breaking down the first section of "Mrs. Crowe's Blue Waltz". As I was writing this, it was a waltz but as it came together it become a "slow foxtrot", which doesn't sound as good.
Here we're looking for drop bends, which means you sound the note already bent and then let it go. It's perfectly okay to feel your way through this by playing the note and pushing it up to find the bend. Ultimately, you should be able to do a drop bend anywhere on the neck. When practicing these, remember that the amount of pressure that you put on each bend is related to the piece you're playing; each piece requires a different pressure.