To practice legato, play scales / runs / atonal whatever using only your picking hand - moving to a new string means voicing the first note with a hammer. Just play anything you'd use to practice picking, without picking :eek:

Sweeping is tricky to master, but it's a knack like everything else, and once you have it down it's easy. Start with playing:

e------7--5-----
B----6------6---
G--5----------7-

The trick is to play the notes in one continuous motion rather than plucking each string, almost like strumming a chord. Do it really slow - and make sure that the notes don't ring in to each other by combining palm muting with lifting the fretting fingers just after the note is played. Hope that makes sense. Muscle memory does it again, so don't go too fast too soon or you'll regret it.

I found minor arpeggios rooted on the 5th string quite easy as a start on sweeping, but again, go slow - every note has to be clean and staccato - no ringing into each other. Use your rhythm (neck) pickup as well. I used a metronome to get it up to speed, but we're talking half notes (2 per beat) at 40 bpm to start...

Work the speed up VERY slowly. It took me 3 months to be semi-decent at sweeping and I'm still developing now after more years than I care to admit...