personally I shake the paint am going to use, use a tad of water in there then use it before closing it so it doesn't dry up then keep them in a cool area. I don't even use palette for painting since it dries too quickly and I keep my brushes in two water containers at all times when painting, one where there used and one for clean brushes. Use only what you need out of the paint container and keep your brushes hair always wet. Am not a veteran, but I've painted an Entire Strike Force of Space marine and Bretonnia knights and never had this issue honestly.
"I am Honored to call every single one of you my brother.....You will die today, I will die today but if we must die for the greater good of humanity so be it. With our deaths, our children will blossom into the stars with the Primarches of anew and start a new, grander crusade in the name of the Emperor and as the Emperor's chosen, we will guide them to that path......Show them the true fury of the Emperor's wraith one last time my brothers!.....Forward in the name of the Emperor and may you find salvation with the Emperor when the end comes for you.
- Chapter Master Nilus Pentis of the Ultra Hawks,
00.? 42M, Second battle of Terra