Do any of the vet tech's in that office know how to express? You could make an appt. with the vet tech, which should be cheaper...
CAROLC expresses Katie. Maybe she could offer some suggestions. BOBBIE- are you out there?
There is no one way to correctly express. You're looking for success to get the job done, however it works for you. If you're not getting all of the urine out, then you need to rethink your method, ask for a reinstruction at the vet's office, or even catherize as a last resort.
Is she resisting your attempts to express? Getting any more movement in the rear legs?
Edited to add: Yes, other people have reported some difficulty learning to express completely. You're not alone. But you CAN learn to do this. Right now I'm teaching my husband to express so I can take a week long trip outta' here.
"How far that little candle throws his beams! So shines a good deed in a weary world." -William Shakespeare