Lay bag flat, cut a slit in the center of the bag, width wise. Lift bag slightly from bottom on either side of slit. Bag should now be two little bags. Cut the connecting paper. Pour each half bag slowly into mixer. Should help. Plasticizer can help smooth the mix but shouldn't be needed unless the pour requires it. Also spray the mixer inside to keep the high sides wet. I usually leave a good bit of water out and add by spraying sides until I get the right mix.