I decided to try again, but this time I used very cheap PVA instead of the decent stuff, and was much happier with the results. The first efforts with decent glue were too thick, the cheap stuff gave a much thinner result - drawback is that the glue itself is much runnier.
Basically, lay the stamp face upwards, and cover with PVA glue - you need enough to cover the image, but not enough to give a thick coat. It's a fine line between enough to hold together when you peel it off but not enough to spill over the edges of the stamp (if it does spill over, it is ok, just awkward getting it off everything, as you can almost guarantee that it will spread under the stamp)
I sprinkled brusho powders over the glue as well, and left them to spread.
Once the glue is dry - it will take several hours, I left mine overnight - carefully peel off from the stamp and trim if necessary. Two of my pieces were trimmed down considerably because the edges weren't thick enough to hold together when I peeled the set glue off the stamp -still, they made nice flowers!
A spare piece using the teardrop ornament went onto the cover of a small notebook, with a piece of leftover brusho card as background