One of the best tips I ever had was for paint pots, after a major paint job there is usually a fair bit left over. So at the end of the job put the lid firmly back on the can ( I put a bit of wood over the lid then stand on it!) put a newspaper on the floor and place the can upside down on it. Now go and clean your brush, when you’ve done that up-turn the paint can and store.
Paint will have leaked into the gaps in the lid effectively sealing the can, now you can open the can years later without having that skin on the top. So when you need to touch up (after the kids doodles) it’s a doddle, I’ve done this after 5 years to avoid a complete repaint.