Hi Michelle, it is possible however it may well introduce extra thickness or uneven thickness to the stem. Also once the paste dries you will be unable to reposition the wire as the paste would break which would mean a lot of forward planning on the formation of your flowers. Hope that helps a little.
Our blackberry leaves mould is available on our website, katysuedesigns.com/collections/chef-nicholas-lodge-collection Here's the link to the tools that he used that we sell on our website: katysuedesigns.com/collections/cutters-tools/products/modelling-tools