Hand pairing butterflies - adult diet info needed

I've successfully hand paired several of the Papilio and most of the Limenitis species in the western U.S. but my success rate is not at a level that I'm happy with. Many times, and even under the best of conditions, the males will not open their claspers and attach to the paired female. I understand that the pre-mating diet of the butterflies is important in order to prime them for pairing. Adding soy to the sugar/honey water mix is known to make a difference, and premixed electrolyte solutions such as Gatorade are believed to help too. I read somewhere that the addition of ash or charcoal is of benefit as well but I'm not sure how you would mix that into a solution. Any suggestions you may have regarding dietary supplements for adult butterflies with pairing in mind would be greatly appreciated! Dale