I am about to order empty plastic bottles to put my mixed acrylic paints in. In order to buy the right size, can someone please let me know how much paint is usually required to paint a model? What is a 'safe' quantity to mix, if the model has separate doors, like the AMT '58 Chevy and requires the valances, wheels, dashboard and various other small bits painted body colour as well? 15ml? 20? 30?