I think something that can help both issues is the use of chromatic, or psuedo chromatic scales. Spanish guitarists have used these tricks for centuries, and it's fairly common practice for them to do chromatic runs to see who is the fastest. Use all four fingers, and alternate going UP and DOWN the strings in the first position (Open.) Then try again at the third, fifth, etc. After awhile, practice skipping strings alternately, for example
1. Low E fifth fret A, Index
2. Low A sixth fret D#, Middle
3. Back to Low E, seventh fret B, Ring
4. Low A again, 8th fret E#, Pinky
5. Low A fifth fret D, Index
6. D string, sixth fret G#, Middle
Etc. all the way UP, then back down. Repeat.
Be creative with these. Develop alternating pseudo-chromatic patterns for yourself. As you descend, pay attetion to how your fingers pull away from the string. Doing these exercises soley with hammer-on/pull-off techniques repeatedly will help build dexterity and correct application. And always, as with all things, safety first. Go slow, and warm up. This is a great way to develop an injury if you're not careful. Then, practice!