I do all of my grass removal and leveling with a sod cutter. I use dirt on a regular basis to fill in low areas. I then drive the sod cutter over the fill several times. I use the cutter with the blade up and blade gear disengaged. It makes a great packer.

Perfectly level and very smooth is a good way to start. The sand should be a very even cushion for the liner. The dirt needs to be flat, level and smooth. It is well worth the extra time.

Best of luck, Dennis