Every time I hit Hobby Lobby or Michaels with my wife I check for colors that look promising. There are some with small shade differences. That way I always have stock colors and don't have to try to match mixed colors. Some would say use a recipe for what I have mixed, but I would lose the recipe or spend too much time looking for it. As for the flow medium, Liquitex is one brand. Art supply stores have various ones.
____________________ Clif Korlaske
OWNER,OPERATOR,CHIEF COOK,& BOTTLE WASHER
"How old will you be before your as stupid as you think I am?"