Fogging oil should not foul your plugs. I fog my skis after every ride because the 951 tends to build up moisture (condensation) in the cylinders (think there is a thread on this) and couldn't tell you the last time I changed spark plugs usually every spring but didn't do it this year.
There is a small fogging port on the air box that you can connect the fogging oil spray tube, but I personally don't use it as I like to actually see the oil being sprayed.