Although I haven't painted anything myself (yet?), I do have an interest. I watch tutorials, I watch showcases, etc, etc.
A couple of weeks ago I ran into the video by Tabletop Minions that's visbible above this post. It evolves about using your paint for a longer period of time without it drying out (as quick).
What is shown is how to make a so-called "wet palette", which keeps the paint humid without deluding it.
- An air-tight box, preferably water-tight too.
- Paper towel.
- Parchment paper for baking (not wax paper).
The box is obvious, the paper towel is used to contain the water, and the magic is in the parchment paper.
Even though it does keep things separated, ultimately it's still porous, so it will magically let water seep through, yet will mostly block the paint to go the other way! It is still being mentioned that the paper towel might get a color as well, but the paint won't run.
So, fold the paper towel into the form that matches the (probably plastic, due to cost and weight) box, cut the form out of the parchment paper (don't fold, you don't want multiple layers) and add water on top of that. Tilt the box so the water reaches the edges of the parchment paper and actually gets absorbed by the paper towel.
After you're set up, use the parchment paper as the palette. Put paint on there, still also add water, paint away, and close the lid on the box when you're done. Voila! Due to the moist on the paper towel, the paint supposedly stays fluid for a long while!
Atom goes as far as saying you can use this setup for up to 3-4 weeks, and that you can reinvigorate it with water after that? I'm not sure the paint will remain usable for the same period, but hey, that might be worth finding out? :)
Please note though, you'll have to transport this in a horizontal state, as the paint might "run"?
Have a good one!