I think that the general techniques for simple composite repairs are shown in AC43.13. Another good reference is Ursula Hanle's Plastic Plane Patch Primer.
You grind out material at some reasonable scarf angle (I'd use something like 20:1 for a non-structural thing like a cowl). Degrease it (I use acetone), and then lay up your repair patches, largest to smallest. For a cowl, I'd cut all the patches so the fibers are +/- 45 degrees to the crack.
Thanks, Bob K.