You don't have to use a solid cover. Many people do use the mesh ones. Some of us don't even cover our pools. I used to but haven't for the past few years. There is a sticky at the top about closing AG pools where you can read about how I close mine.

As far as a sand filter goes --- remove the plugs and drain it. You can leave it outside if you want. But, you will want to remove the gauge. Those things break easily.

Glad to hear that the forum helped you enjoy your pool this summer!