Not to mention you should not put a steel ball into a glass bottle. Trust me. In the 90s, Revell used to sell airbrush-ready enamel paints that already came with one in the bottle. Two of those bottles broke in my hand as I was shaking them, luckily without cutting me but with paint flying all over the place. After the second, I kept using the paint but carefully took out the steel ball from each bottle immediately on first opening it.

As for other paints in bottles or tins: I stir them with a cocktail stick (if the bottle or tin is small) or an ice lolly stick (if they're the size of Tamiya's 10 ml bottles or bigger). This works better than shaking, and is the only way to get things mix for tough paint like most enamels.