Thanks Simon, that helps. I'll make sure I'm in the auto shop, not the pet shop. ;-)
I was about 25-30cm away, spraying parallel as you suggest. It was indeed going on dry and powdery, more of a misting that getting wet.
I suspect I was just moving too fast. When my kid had a go he got one stripe nice and wet, which at the time I thought was *too* wet. But it looks like that bit is actually what we should have done all along. He was a fair bit closer and it was a narrow stripe (3cm wide?) that went on quite wet.
Oh well, it's all a learning experience. I'll sand it back a bit and redo it. Slower and more of it.
Next question... when sanding, I'm using 400 grit, with water on the paper. It makes a nice slurry. Do I wipe that off the guitar as I go? Leave it on? With the texture of my primer coat at the moment the slurry is drying in the little bumps. Maybe it won't be a problem and will wipe off easier when I get the primer coat on properly?