I have always used a "California Car Cover" product to cover my cars. The cloth type with the soft flannel inside. It has never scratched the paint and it breathes. Great for inside storage. The nice thing about my cover is that once a year (Spring) I wash it and run it through the dryer. Comes out like new and tighter fitting.
As for winter storage,I place dessicant bags throughout the interior , trunk, and engine bay. I place these bags on paper slips everywhere. The bags I have are 1/4 lb each and work great in trapping any temperature change moisture. In the spring, I remove the bags, dry them in the sun on the deck, and put them away for use in late Fall.