Something I do a lot when mixing is to take the backside, not the receiving side, of old film positives or carrier sheet trimmings (a pc of glass would be good too) and use it like palette to test a few different combos are feel out how strong one color to the rest. Next put a little of the mix on the egde of a clean knife and scrape onto test material to see what it's going to do on your shirt color. Start there and then go to mix and jot down your %s in case you run out of ink mid-run and forgot what you did to mix that color. Prevents you from mixing a whole quart of ink that looks like baby poo.