Any car in garage storage, IMHO, should be totally covered in NEW Pure Wool unwashed blankets ideally almost to the floor. Ideally, a tailor-made Cover out of these new Blankets would make short work of "on/off time", but I still haven't done it. Would save time draping blankets one blanket at a time.
The natural lanolin is a perfect rust inhibitor, as I have found whilst storing cars for the last 30 years, and highly recommended by several auto experts when I was young lad, and also more recently in middle age.
I always drape my weekly/monthly collectables too, as this obviates the need to wash the car more than 1-2 times per year, as the blankets keep the car eternally clean. The 1-2 times a year is also via "dry-cleaning" as detailed next.
If a weekly or monthly outing results in light soiling, "dry cleaning" with a body cloth and weak car-wash followed by a chamois constantly rinsed in clean water, seems to work really well, and avoids water ingress into areas you have no way of drying.
Moreover, pure wool blankets always used the same way up, are the least likely of all to scratch your finish.
A good thrashing of the blankets whenever time and weather permits, will keep them from collecting excess soil caused by airborne dust and fly-poo and spider-poo.
The blankets have definitely saved some of my stored & every-day cars from "little accidents" in the garage
 
Apparantly this procedure is recommended for any finish; old or modern paint chemistry

Certainly has its merits. When my car was being built I went to Vinnies and got some king size quilt covers for about $10 and used these to keep general dust and crap at bay. I did upgrade to a proper car cover when complete and did a lot of research and " touchy- feely" at local automotive accessory outlets before choosing the softest non-scratch material I could find. I find it difficult to get the cover in position at the start because it keeps wanting to slip off my beautifully waxed clear coat. Vinnies can also be a good source of quality woollen blankets as well.  If you have access to a sewing machine/ operative - aka wife, missus etc then sewn together for complete coverage is a cheap option.  I think the humidity up here would not do well, I would have to keep washing and airing them out. Len

Len, re humidity, I would seek advice from a WOOL expert, which I'm not. From what I have gleaned from others more knowledgeable than I, WOOL is very diverse and has amazing properties. Fireman and racing car drivers used to, and not sure if they still do, depend on woollen under-wear as well as outer wear, for being the most useful material even in humid conditions or being drenched by fire hoses water and/or mist to heavy spray, which in turn result in high humidity.
If I'm wrong re humidity/FNQ/wool , then possibly 100% cotton, as in bed sheets, may be your best bet.
Used blankets are not recommended, as there's no easy way of telling how much protective "lanolin" has been washed or dry-cleaned away.
Let me know when you find out, as I'm very interested
Cheers..............Bernie