Painting some very completed and detailed bushes or leaves over oil paint can be a very hard and challenging job where the results often are very disappointing and way too dull.
Not so difficult to do and with much more spectacular and dazzling results would be to paint this in black gesso on the canvas before you start.
First, you need a plan in mind where you wanna plant the bushes and where to locate the trees. If any ground level, paint that first with any desirable brush. Then add the major tree trunks with a script liner or filbert brush. After that, you can implement the various bushes on the ground level and leaves on the trees by taking a piece of (strong) paper towel. Fold the towel roughly together and dip it into the black gesso.
Start with a dense bush first since the first dip on the canvas will leave the most paint on it, or else dip the first one on your palette or another piece of paper towel to get most paint off. Then tap further on the tree trunks for some leaves or above the soil for some bushes. The more you tap, the less paint that will come off but even the slighest tap will create some very tiny sparkles on the canvas. Reload your paper with gesso and continue to form bushes and leaves until you are satisfied with the result.
Finish off by adding extra branches or similars with the scriptliner and then leave the canvas to dry completely before you can start painting over it. Remember to only use TRANSPARENT colours over the black gesso to give it its maximum effect.
This idea was given to me while painting Bobs' work 'Deep forest falls', Season 28, episode 8. There was a need to create some trees and bushes in black and grey gesso. Bob uses mostly scriptliners for the trunks and branches yet some tissue paper for bushes and leaves. The effect was amazing and I gave this a go at one of my African paintings.
And the painting looked like this after it was finished:
Please let me know what you think of it or how you managed!