Q: how best can I coordinate my left-hand vibrato with my right-hand bowing?
A: i think you just bow steadily and do the vibrato with your left hand? i'm not sure i don't play any bowed instruments. but this is the kind of thing you will surely learn naturally the more time you spend enjoying your instrument, and playing what you want to play. and then soon people will ask you how you do the vibrato thing and you will have no idea how to explain it