Didn't wanna add this to my original post cause it would end up PAGES long, but have also found that it's fun and also beneficial to play along with vocal lines, and also other instruments. I do a lot of this, and find improvising over whatever it might be LOTS easier as a result. Really try and mimmic every naunce of the singer's vibrato and stuff, or whatever the instrument might be that you're playing along with. Has helped my vibrato out bigtime over the years, to the point where I'm pretty happy with it.
Probably something ya's all do already to a point I dunno, but if not, I'd recommend it.