I assume you are talking about cantilever brakes. One thing that I have found that makes it much easier to do a quick release is to get a straddle cable that has a removal pull tab like this one:

http://www.biketoolsetc.com/index.cg...id=JW-SC380TRI

There's more to look at here:

http://www.biketoolsetc.com/index.cg...dle/Link-Wires

Without a pull tab, the easiest way to take the slack off the straddle cable so that you can get the barrel
anchor released is to reach through the wheel with thumb and forefinger to squeeze the pads together. If that does not do the trick then you probably have your straddle cable too tight or your main brake cable needs a little slack put into it.

Hope that helps. Best luck!