more vibrato questions

["alciere" <alciere@xxxxxxxxxxxx>]

In Paul Butterfield's instruction video he has sheet music with a zig zag 
line over the staff. I know it means vibrato, but are the notes actually 
bending-vibrato or am I just modulating the volume-tremolo? 

Also, I can do diaphram vibrato albeit slowly. When I do this while bending, 
I have to use my throat, as my throat is doing the bending. Is this how it's 
done? 

Thanks for your help. 

Update on practicing. I've put in a half hour a day on just vibrato. The 
vibrato is a little better, but nowhere near up to speed.It's also hard to 
hit a bent note correctly with vibrato-there's always a little delay before 
I can get the vibrato going.I also can't go from a bent note to a normal 
draw and keep the vibrato smooth. 

Rainbow Jimmy