I know about steaming gum paste flowers to get the colours to look deeper, but is there a way to get them to stay shiny?

You could try gently brushing them with thinned piping gel to give them a glossy look.

They make an edible lacquer you can use. Pearl/luster dusts would give a bit of a satiny shine as well.

A mix of gum arabic and water will work as long as you haven't colored the flowers with dusts (it makes the color run). Confectioner's glaze will work over dusted flowers. In a pinch you can paint them with a mix of tylose and water...ever notice how if you end up with a drip of gum glue, it's shiny?

Thanks for the posts. I think I will try the gum glue. I have not dusted the flowers but I did colour the gum paste with gel colouring. I hope that won't matter.
Thanks!

Add a little vodka to corn syrup and paint it on the flowers with a paintbrush. This gives a glossy look. I used water instead of vodka tbh and it still worked although I may have had to wait longer for it to dry.

I did a trial using the gumpaste glue and it looks very streaky lighter in areas and darker in others. Will using the vodka and corn syrup look the same as this?