As a followup to an earlier post, I wanted to report that I've had a lot of luck, and saved a good deal of money, by using Dick Blick acrylic paint ("Blickrylic") instead of Golden's. Of course, the colors aren't luscious like Golden's. But for "no-show" or covered areas, like toning backgrounds and my initial applications of white lines, it works great.
Nothing can replace Golden's Nickel Azo Yellow, though! It comes out a rich golden brown and dilutes into a sizzling hot yellow. Not a tacky, screaming yellow like hansa yellow or certain cadmiums can sometimes be. But Blickrylic's brown and yellow mixed together can make a series of lovely forest greens.
I've also had luck with diluting the Blickrylic into Golden's "fluid acrylic" consistency by mixing in water and letting the mixture settle overnight. By adjusting the amount of water I add, I can get thinner or fatter lines, as detailed in this older post.