What scale to use for supertonics?

[phxlbrmpf]

One of my band's songs is in F major and the last chord before the bridge , which is in C major, is a G major, which sounds pretty cool.
Thing is, I'd love to play a cool descending run or something over the G but I can't seem to come up with something that sounds good. I tried the G7 major scale, but didn't really like the result. Even pentatnonic G doesn't sound "cool" here for a change.
I've never come across a lot of supertonics in my "career" so far, is there something like a scale that sort of "always fits" when played over supertonics?

I'm thinking of trying a chromatic, descending run from the G next, it kind of seems to fit to the tension the supertonic creates. The song's in 6/8 time, by the way.

[seanlava]

Since the supertonic chord is a secondary dominant, the dominant scale (myxolydian) will fit perfectly.