Johnny,
Welcome to the forum. 6# of DE is a lot of DE and I can understand that it would probably clump if not premixed. I routinely add about a cup to my sand filter and I premix even that little amount because I believe it provides a more even coat on top of the sand. Whether it could cook a motor is debatable as I think you should see other signs of a problem like reduced or blocked water flow, excess noise, or something, before it cooks.
Al