I do have a great way to store paint and had to figure out something since I can't always get back to a large painting and sometimes I"ve mixed lots of paint! So, there are two ways I store paint, and one is the Masterson Palette - you may already have one - it is usually used for water based mediums (there is a yellow sponge you can wet that keeps acrylics and and watercolors wet) but I don't use it for my acrylics, I use it for my oils/cwm. I put leftover piles of paint on freezer paper (or palette paper) into the plastic box, cover with saran wrap, and then put the yellow sponge over the top of the saran wrap with several drops of gamsol in it (may 4 TBSP or so - or perhaps a little more, depending on how long it will be sitting). If you have an old refrigerator or one in your studio which you can dedicate to storing this Masterson palette, that is where I keep mine. It keeps the paint fresh for a long time and I checked with Gamblin and they said it was ok. My husband made a nice wooden lid with a handle that replaces the plastic lid - just because the plastic lid is not always easy to get on snugly. Here is the Masterson Palette with lid and sponge: https://amzn.to/
The second solution, if you don't have too many colors to store, is these tins: https://amzn.to/2YTuA1R
I almost always store my extra cwm/ggel in the tins even if I don't store the paint in them. If paint does dry out, just use citrisolve to dissolve the paint over nite and then you can wipe it clean and use again.