The 4 note "thought" is a good one. Take a Major scale and break it down into 4 note segments. Play the first four notes in the scale, then start on the second note of the scale and play the next three, and so on. In other words 1234, 2345, 3456, 4567 (notes from the scale, not frets). Then work it back down 7654, 6543, etc. This will get you working across 2 strings for each segment. Tie them together, alternating your pick on each note, up, down, up, etc. Try starting the runs with both an up or down stroke to get the feel that works.

Create your own exercises.