Time to test out kiln wash vs using papyros paper as ultimately this has got to be the most economical way forward. Mixed 1 part bullseye kilnwash with 5 parts water and mixed up in an old ice cream tub. I then used the largest of the goats hair brushes I’d bought from Amazon to apply 5 coats (up / down/ diagonal/ diagonal/ up) as per instructions and have left the shelf in the kitchen to dry (I believe this should take 24 hours). I’ve resisted drying it in the kiln as I’m still not too sure about whether you really should put damp things into a glass kiln for drying so I need to read a bit more about this first. I’m going for a natural dry on this occasion.
Update – this was used in my next firing and it was completely successful as no glass items stuck to yhe shelf. Interestingly though the pink glass (on the face and hands of the little figure had kiln wash stuck to them, but nothing else did). I did decide that because of this, I would not risk a second firing without scraping and re-kiln washing the shelf.