after I drill out the access holes for the needle valve,EZ fueler,etc... I will enlarge them with a fine round file so I don't burn too much of the cowl with my dremmel even at low speeds the motor tool can open up holes fast with the file you can tweek the hole if its a little off center and there alot more control.
I will then use Blue tape too cover the holes on the outside of the cowl and re-enforce the holes with epoxy on the inside,trimming away the exess with the file after its hardened.
epoxy sticks well to the interior of the cowl and stifens the holes