Grist Hydrator is an useful device for the MLT that wets your crushed grain when drop into MLT,it is used to minimize doughballs in your MLT.

Doughballs keep the hot water from mingling with a portion of your crushed grain.  

If the hot water is not able to access all of the grain, 

it will not be able to effectively activate your enzymes for conversion,using a mash paddle can also help to get rid of any doughballs in your grain.