Besides messing with motorcycles, I do a bit of woodworking. I prefer using oil-based finishes on the woodworking, bikes and cars. Don't chuckle... California is pushing legislature for aqueous-based (as in
water) automotive paints.
It never rains in California... you know the tune.
I hate wasting finish materials when they skin over in a half full can. Gets pricey. I have used a product sold through woodworking supplies that is an inert gas in a rattle can. Just before slamming the lid shut, a 3-4 second blast of
Bloxygen is injected into the can. The gas settles over the surface of the liquid thereby keeping oxygen away from the paint, varnish, etc. It really works.
At ten bucks a can, I feel the Bloxygen is high priced. After chatting with a fellow woodworker, he shared that he uses a quick shot of
propane from his torch bottle. That's what I'm now using and it works.
Safety warning & lawyerly stuff: Don't smoke when doing this. No open flames. Don't do this in your laundry room closet as you may gas yourself. Basically, take the same precautions you would do prior to breaking wind at the Christmas dinner table.

I'm about to shoot color on the '83 R65 and a quart of color is the minimum buy. If I get sloppy, I may use half. At least I'll have some for future use that won't be dried in the can.
Monte