Mike:
You can buy empty paint tubes from Daniel Smith. You can fill them from the back and tap them on the lid to seat the paint down inside. You then fold up the end and crimp it with a pair of canvas pliers.
For my grays, I mixed and tubed nine values using Flake White and Mars Black. I mixed a tiny amount of yellow in to kill the blue and make them more neutral - Raw Umber for values 1-3, Raw Sienna for values 4-6, Yellow Ochre for values 7-9.
For my baseline flesh, I mixed and tubed nine values of flesh from dark to light. I began with Yellow Ochre, Red Ochre, Titanium White, and Ivory Black. Bought new tubes of all from Old Holland.
I mixed equal amounts of YO and RO. This made a good value 3 base for me to mix everything else from. Mixed the value 3 with ivory black to create two darker values 2 and 1. Mixed the value 3 base with titanium white to get values 4-9.
I think I bought four tubes of everything and then used it all up to create nine tubes of flesh. You will be working with BIG piles of paint. You put them into the tube with a long palette knife.
In practice I have found that this palette is too bright and needs to be knocked down in intensity a bit. For this I use my neutral grays. I mix a little of the corresponding value gray into the paint nut to neutralize it a bit. You could easily add some gray to yours when you tube them. I have thought about squeezing mine all out and fixing them to my tastes, but that would waste tubes and I am too stingy.
