So, here's what I did with one to show you how flesh them out with leaves.
I put some green on the branches of the Woodlands Scenics tree armatures that I coated in my modelling paste mixture. I used pieces of seafoam flocked with some Noch leaves to attach to the tree trunk.
These last two photos show some Birch trees I am making. They are simple twisted wire armatures, covered in the paste. The bare tree was painted white.
I'll tone down the white with a thin brown wash and then put in dark speckles with a fine point magic marker. After that, I'll add some branches with leaves. You can see the finished product right next to the bare tree.