developing a good
legato technique is very hard and takes a lot of effort, when your accending, just pick the first note and play the rest of the notes using hammer on and pull offs, however, when decending try hammering on to the note with your fretting hand and not picking the first note at all, this is like the primary rule for smooth legato playing
I think you should learn some parts of the solo in Satch's Devil's slide, that song really helped me develop my legato skills
and make sure you stop doing the legato licks when your hand starts to hurt !