Because the leaf skeletons have open veins, the other techniques did not create clear impressions. I tried a couple of different approaches, and found one that worked. The best effect resulted when I used a small mop brush, with most of the powder tamped off first. Then I dabbed with the brush instead of drawing it across the leaf. This allowed the powder to go into the open spaces and not behind the thin lines of the leaf veins. The samples here show the results.
I started with the red, heart shaped pieces. This is where I discovered the need to dab rather than wipe with the brush. The heavy gold along the bottom piece is a result of too much powder on the brush close to the edge of the skeleton leaf.
The blue and gold pieces above turned out the way I wanted because I used very little powder on the brush and used a direct down and up "dab" motion for application. Now I just need to find more leaf skeletons.