panda,
u can only massage the back part of the breast cos the shield dun cover the whole breast mah. it does take a bit of practise. let me see if i can explain. u using double pump right?
ok, so left forearm 'kiap' left shield onto left breast, left hand hold right shield to right breast. so yr left arm is across both breasts. use right hand to massage right breast. because u're using yr left hand to hold the right shield in place, the connection should not break so easily.
to massage the other side, just mirror image the above. so right arm kiap right breast, right hand hold left shield, massage left breast with left hand.