How to store paint so it stays good?

[FlippinFriday]

I have a half used tin of F&B floor paint. I'd like to store it well so I can use it for touch-ups in the future. But my query applies to any paint I guess. How can I best store it? The lid doesn't fit on well now I've opened it a few times but I haven't tried a mallet yet. Some old guy once told me he stored his half used tins upside down to stop the air getting in. The other option is that I decant it into some other container - maybe like a food storage box? Any ideas?

Hammer the lid down as best as possible, seal the top with duct tape. Store anywhere you like, ideally off the ground to stop it getting rusty. It's an oil based paint so shouldn't dry out.

Put cling film over the tin before you hammer the lid back on.
Recently opened a tin of oil-based paint ten years later—after peeling off the 1" crust, the paint underneath was still good!

metal tins don't last well.

plastic tubs are better, because they re-seal tight, and don't rust.

A painter and decorator told me to pour spare paint from any tin that was less than half full into a clean glass jar and label it to keep for touching up.

Jam jar/pasta sauce jar (labelled clearly!)

It's water-based if that makes any difference? & about 1.5litres

water-based paint will make a tin go rusty.

Stir it very very thoroughly and decant into large glass jars (such as are used for pickles) with a tight screw lid. Fill it as near the top as you can manage (an air gap will encourage a skin)

Use jars of a size that, once opened, you will use the whole amount. A half full container will skin and go hard.