Definitely no fill on the fret slot ends. No sharp edges of frets that catch, but not 100% smooth. I am now thinking that I could sand the current edge smooth (sanding back onto the neck somewhat to get some mechanical adhesion), tape the fretboard top and then spray the sides.
Or maybe, as Joe mentions above, I could leave it as is for now to avoid losing momentum on the build. Once I have a playable guitar I could always pop the neck off and spray the edges then.