Watch the Whole Step Bends online guitar lesson by Jeff McErlain from Blues Guitar Survival Guide - Lead
A great way to practice bending is to fret the pitch you want to bend from, then fret the pitch you want to bend to. Go back to the original note then bend it up to the pitch you played previously. Really concentrate on the bend being in tune and make a mental note what the bend feels like physically. When we think about these actions and concentrate on them the mind - body connection becomes stronger. I promise you will get better at it faster. It's like sports, if you want your jump shot to be better, you have to practice it with focus. I apologize for the sports analogy, I think the main reason I took up guitar was that aI was so poor at sports!