I've installed Invisible Shields on all of my BB's since the 8700 and have always used the included spray. If you get the pieces wet enough to slide them around you'll be fine. The biggest concern is not getting the water indicator (IIRC in the battery compartment) wet. I've never done so on any of my BB's. Still, go with what you're comfortable with.
You don't need to get the pieces soaking wet.