Lay out a tarp on the floor where you will work. Set your bucket of drywall mud on the tarp.
Add 1 cup of water to a 5-gallon bucket of softened drywall mud. Mix it with a manual drywall mud mixer until it reaches a new, softer consistency.
Add more water until it is a little thicker than house paint. Add the water slowly to ensure you cut off the flow at just the right time. The mud should cover your roller in a thick coat with hardly any dripping off the roller.