Here's one that worked great for me for the fretting hand but only do it for a few minutes at a time and then break when you're first starting out. (Not for the faint of heart or those with really short fingers though).

The concept here is to keep alternating between picking the 6th string and then the 3rd and 1st strings together with a combination of the thumb, ring and baby fingers...creating a boom-chuck kind of thing.

In standard tuning, fret using the thumb on the G (6th string - 3rd fret) and keep it there no matter what.

Play that fretted 6th string with the right hand thumb, then with the index and middle fingers of the right hand, pluck the 3rd and 1st string with the pickin' hand beginning with the index on the 1st string/3rd fret and the middle finger on the 3rd string/4th fret. Repeat this pattern, but the second time after playing the G bass note with the thumb, move the 4th/ring finger to the 3rd string/5th fret and the baby finger to the 5th fret/1st string (keeping the thumb anchored on that G note) and then move the ring and baby fingers up one more fret (same strings but now on the 6th fret) and again to the 7th fret, and then walk it all back down to the original starting position...and just keep repeating.

So you're getting a bass note followed by the higher two strings played together and just repeat the entire process, making sure the keep the thumb fretted and anchored to the 6th string (G) and moving up the other two fingers on the 1st and 3rd strings progressively and then back down to the positions I've mentioned. I hope this is understandable.

It is a bitch and it hurts when you first attempt this...so take it easy and just do a little at a time, and in a matter of weeks, you will be amazed at how your reach has exceeded your grasp. **G**