A friend of mine once introduced me to this briliant invention: Self-watering brush!
You can find it at Popular, but the one I bought was from Art Friend Plaza Singapura. It cost me $12 for the set of three types of brush. Worth buying 👌.
It has a water container in which when you pinch it, it will drop water into the brush. All you need is a pallete of dry paint and a paper medium, then you’re ready to paint.
It’s very traveller friendly and minimum mess. Almost no spillage except when you pinch the water too much. Other than that the boys really love it as much as I love how it gives me less cleaning up. 👍👍