just double checking im doing this right?

So i poured 20 gallons of Ro/di water in my 30 galloon tank (for water changes). I placed a powerhead made for a 40 to 60 gallon tank and a heater, when im off work, im gonna add cup by cup slowing in the tank, and just let the powerhead do the stirring? and i plan on letting all that stir up good for 24 hours before adding to my tank?