Well, fellow newbies, I have a solution. I was very kindly gifted with enough gold and silver powder to last me a lifetime, so I have felt I am able to experiment with it. Here is the first experimentation: a basic side-by-side comparison on piece of scrap paper.... I used a modern gesso by pebeo, which is in effect a PVA glue. Leave to dry for 15 mins, then simply dip the very tip of your brush into the powder and lightly spread over the surface. You only need a TINY amount - I learnt that lesson quickly! (First time I used it, I treated it like glitter - tip a bit onto the gesso then tap excess back off into bottle. Needless to say, I only did that once!!)
Tip for money-saving - you don;t need an expensive burnisher. If you do want to bring up the shine of the powders a little bit more, you can use the back of a spoon.