On these I used a dowel sharpened to about 1/8" at the tip dipped into orange plastic and then dabbed in the mold cavity right behind the gate opening. The dowel is about the diameter of a pencil and is sharpened using a pencil sharpener. It takes some practice so try dipping and dabbing on the mold using junk plastic that's been heated up. Once you get the hang of it, get out the serious colors and go for it.