Keep extra files around like people mentioned, they work wonders. I keep a coarse and a fine in the trailer at all times. Also keep in mind with the filing, it's meant to extend the life of the plug, but it still has a finite life.
Another note, my most recent viton o-rings seemed to be stiffer than my last batch. I found I had to push in harder and twist while disconnecting my QDC's, just to get the coupler sleeve to slide. Like most repetitive things, it's now almost second nature to disconnect them now.