We would recommend using a blender. Slightly staler bread will process better than very fresh bread. We would advise that cubes of bread (crusts removed) are dropped one at a time through the hole in the lid onto the revolving blades. Once one cube is processed the next can be added.
If using fresh bread you may have to stop and empty the unit at intervals because the unit will clog and unprocessed bread will sit on top of the blades. For small amounts you can also use a mini chopper but care should be made not to overload the unit.