is there any practice methods to get that killer bluesy vibrato... especially when bending

The best method for practicing is to practice a lot....sucks don't it.

I learned blues vibrato by listening to great players and then trying to emulate them, but so much depends on the guitar, your fingers and the amp you play on.

Great vibrato is like eating Mexican food with salsa. The vibrato makes an ordinary note sound extraordinary. But each player develops their own style, it is part of what makes each player sound different than the next. Nobody has the tone I produce and I cannot match anyone else tone 100%.....It's in the fingers and a matter of personal style.