Soft99 Sanding Cube
By just using this cube in the right order, the surface preparations will be done, because the 4 different sized grids are arranged on each of the 4 aspects.
Also, instructions and grid sizes are printed on each aspect, which allows beginners to use it with ease.
Furthermore, you can wipe off water drops with it.
Directions to use
* Apply onto the surface, wetting the area that will be polished.
* Change the aspect as needed, following the instructions.