The set of dually's I got came with a switch and relay pre wired, but I wanted to do the same as you. I used the stock fog light circuit to fire the relay that came with the D2's. I think I may have had to run a wire down to the fog locations, I can't remember for sure.
How I did it was to not use the switch that came with the dually's, there is a blue? wire the best I remember that goes to the D2 switch, that is the trigger wire to the D2 relay, use that that blue wire that was connected to the switch and splice it into the JK fog light circuit at the lamp location. I cut off one of the factory JK lamp plugs on one one side to make the connection to the relay trigger. Cut and solder if you can, if you can't, use some good quality crimp connectors and tape them up well with good electrical tape. Cheap stuff never sticks well. In the pic you can see the 86 terminal is your trigger input. That is where the stock JK fog light circuit will land, and all other connections are the same as far as positive and negative. The D2 lamp power will be from the battery directly, so your stock switch just activates the D2 relay, which them feeds battery power to the D2 & the canbus system is none the wiser and no goofy flickering will happen with your new fogs. Hope this helps. Let me know if you have questions, it's pretty easy really. I wish I could verify wire colors for you, but my jeep is at my office at the moment.