tape one color first , then tape the second color and when you want a flame lick from the top color to appear on the bottom of the bottom color just stop in front of the lick and start up again after the lick so it gives an under appearance . it sounds confusing but once you figure it out it is really easy
If you're overlapping the same color,mask it to let them cross.After you untape it tape off the one on top and the sides of the bottom one so the top one is covered and the bottom one is exposed.Then mist a touch of really thin black (or add black to the color to darken it) over the taped off top lick.When you untape it the top lick will have a shaddow on the edge and give the illusion of being over the other.Hope that made sense.
