ORIGINAL: Steve Percifield
Buy some of the beaded chain that is used on pull/pull ceiling lights. It's the little brass ball stuff. You can get it at any hardware store. Stand the wing on end, insert the chain and shake a little. The chain will find it's way through the wing rib holes . Tie the servo lead on and pull it back through. This chain makes the job very easy.
I didn't think anyone else did this. If I build I put the string in before covering but this is really the way to go for an ARF. I have a long piece that I salvaged out of some old vertical blinds we pulled down during a renovation.