One of three I had to spray this past summer. 2x6 rafter for reference.
At least you could see the darn thing to spray it. The bastids set up shop by the entrance to our house, but there's a ~6' deep covered eave so I have no idea where the nest is to and spraying the entrance several times didn't do the trick. Nor could I find it by running a cheapy usb endoscope into the hole they were accessing the nest from. I will be plugging said hole now that they have quieted down for the year.