Took left flap apart again and deburred.
Tried something new. I borrowed an airbrush from a fellow builder (Kevin) and mixed some Cortec and water and sprayed the inside of the flap. I then brushed the edges (1" foam brush). Worked great! It made it so I didn't have to reach way in the flap skin to get the inner-most holes, though it did aresol some (it's what I wanted).