I didn't have much luck with the trigger thing for spray cans. I found I was better off with just a finger, and a glove on the finger. I used something much less elegant screwed into the pickup cavity to hold onto and move the guitar while spraying. I suspended from a tuning machine hole.
It looks like you have what you need. The only thing that I can think of is that you might want to have something to grip at the other end of the guitar. With luck you won't. But FWIW if you do....
I made this from found objects around my house be able to grip the headstock without messing up the paint...
Not a very clear picture... The wood is a piece of dowel about 20 cm long. there are two compression washers made of hard rubber that are the only part that touches the finish and only at the very edge of one tuning maching hole. You can't see the threads clearly but the silver in the center are threads from a hanger bolt:
The "nut" is made from a T-nut and an older wooden knob. You could use a wingnut or conventional hex nut if you wanted a smaller footprint for spraying.
Not elegant at all. Made of found objects around my house...but it worked pretty reasonably well.