Using a pug mill to process your clay will help it to have a good consistency. With pug mills, clay is fed through the hopper, packed with a tamper, and churned with an auger to work out lumps and inconsistencies, pack it together and pushed out to be stored for later use. Be sure when you are getting clay off of a plaster bat, you do not remove any of the plaster with the clay, as plaster is a hydrous material that holds water.  When fired plaster will explode ruining any sculpture that it is embedding in.  You still need to prepare the clay for use by hand after putting it through a pug mill, however pug mills greatly decrease the amount of time needed to prepare your clay.