I wonder if anyone can help me. I am new to Maya and experiencing some problems when attching a blend shape surface to my character rig.

I have a character all rigged up and Iam now creating the blend shapes for some facial animations but everytime I move the blend shape slider to animate the character surface moves back to the position it was in when duplicated.

I then decided to dettach all surfaces, create the blend shapes and then skin the character to the rig. This solved the moving back problem but just created other problems though - now when I rotate the joints the surface stretches and deforms out of shape.

Is there a general rule of thumb when using blend shapes with a character rig?

Please help????