Yesterday's enthusiasm for Pripp's flux is somewhat diminished now, since the stuff seemed to wreck the spray bottle I'd put it in. Sigh.
However, this did mean that I finally tried the Cuprinol I'd bought a while back, and that worked very nicely indeed. It's got a perfume-type atomizer, and that's a huge help. It wasn't any more persistent at 1500F then the Pripp's- but it wasn't less persistent, either, and I'm confident it'll work very well at lower tempt, plus being easier to apply (for me, now).
Once I've used up this bottle of it, I'll get another and try the Pripp's in the old bottle, though!