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a. This is the part where you kind of have to play it by ear.
b. As it is the Rays layer is really light, almost invisible. To make it more visible make a copy of it by dragging the Rays layer into the new layer button
c. Then hit Ctrl + E to merge the two layers together.
d. Next hit Ctrl + F to repeat the Radial Blur filter.
e. Repeat these steps until the Rays layer is the size and brightness you want.
f. After you have the Rays layer the way you want it go to Filter>Blur>Blur More to degrain the image a little bit.
g. Next click on the Crack layer, click on the left side of the crack with the Magic Wand tool. Then click on the Rays layer and hit backspace to clear the selection. Finally hit Ctrl + D to deselect.