Bill Tindall
This stuff was developed under government contract as a waterless hand cleaner. To emulsify a hydrocarbon (kerosene/mineral spirits/etc) one needs a surfactant. Tecnu has a surfactant that accomplishes this task and so does every other hand cleaner based on an emuslion of a hydrocarbon solvent.

To get the poison ivy juice off the skin, or possibly extracted from the outer layer of skin, requires a good solvent for the urushiol, which is a mixture of oily allergenic compounds. Additionally, this good solvent must remain in contact with the skin for some time to allow for solubiliztion and perhaps extraction. Then the hydrocarbon must be easily washed off the skin taking the urushiol with it. The process is no more complicated than that.

Both the hydrocarbon and the surfactant will be good solvents for the urushiol compounds. So is toluene and alcohol and a bunch of other stuff, all of which will evaporate too quick to be best at removing the urushiol. I don't know if one surfactant would be somewhat better. However, the sea of hydrocarbon will be the main extraction solvent I would predict.

I would expect pure surfactant to work just fine, but it would be very costly to offer as a consumer product and it could cause 0.000001% of the population some problem if not used properly.

The linonene in Fast Orange will be an excellent solvent but this expensive solvent may not be present in high concentration in Fast Orange. I don't find that fast orange is as effective as stinky Gojo at removing "car fixing grease" so it is a reasonable assumption that it will not be as effective at removing urushiol.

The bottom line for me is that anything that removes old car grease is going to be effective.

If you want to try more concentrated surfactant then go to the Ag store and buy surfactant concentrate for emulsifying Ag sprays. A gallon will only be few bucks. Personally, I'm sticking with Gojo.