Re usefull practice away from the guitar:
Try drumming your fretting fingers in different rhythms and combinations. At the most basic you can try:
1234, 4231
123, 321
The above is easy but still very usefull for developing speed and agility...

But the following ones are seriously challenging and will mess with your head for ages:
1324, 1324
4231, 4231
1423, 1432
4123, 4132
The above patterns are deliberately confusing and the same principal behind Progressive Matrices you might find on a tough IQ test.

These excercises really helped me a lot, they are very awkward and get your neurons firing - when you can do these without losing rhythm and pattern then you will find things like sweep picking and string skipping a lot easier when you get to that level.