97 A6Q rear brakes

[walian at att.net]

Hello all,

 I am attempting to replace the brakes on my A6 and
can't seem to get the piston in the rear calipers to
push back so I can insert the new pads. I noticed the
the bently mentions to use a special tool which
requires turning 2parts. Is this required? Should it be
like older brakes just open the bleeder screw in the
back and force the piston back using a tool. ( I have
drilled and tapped an M10 through one of the old pads
and then placed the other pad in the to push against
the piston when I turn the the screw.) This doesn't
seem to be doing to much, am I just not applying enough
pressure?

Thanks

Frank