1. You should balance upwards and downwards bending for vibrato. I know that downwards is easier (I'm always doing it) but for the 1st string you need to do both XD
2. Yes and those vibrato bend is the most expressive technique for me (that's why I love Galneryus). The technique there is to push the string up (just like your normal full bend) then release the pressure on the string. Do not force the string to go back...just let it go down by itself. Then you need to push up again. Rinse and repeat.
Souryu's cover of Don't Say Lazy uses vibrato bends frequently and beautifully:
http://www.youtube.com/watch?v=5MPcVlh6uEs