George,

There are paints which with some fool the eye application tricks will work
pretty well from a distance.   Suggest you try using a colored undercoat to
imitate those used under real leaf (red or ochre for instance).  On flat
areas you can do slightly overlapping rectangles which imitates the
overlapping of sheets of leaf.  Be sure to let a little of the base show
thru and then add a wash to imitate what ever color of patina, etc. is
appropriate for your application.

A Cuz