I don't use a fan brush. I keep it uncomplicated and use what ever brush I have in my hand at the time. I only use three brushes in watercolors. A 2 inch flat brush is the one I use most of the time. It's easy to fan it out if I need it to. I can make skinny lines and wide strokes in just the way I turn my brush.
Definitely do not paint individual blades and they don't have to be shades of green. Keep it simple. Use more water than paint. You can splatter paint too. It adds a nice affect. Tap your brush perpendicular to the side of your hand and splatter where you want it. You can also use a tooth brush. Just dip in paint, aim it where you want it and run your thumb over it. I know someone who paints on a screen to get splatter. Don't worry if it goes outside of the area you wanted it unless your painting clean washes that you want to remain clean. Also lifting with a dry brush in almost dry paint. You can also scratch the paper while it is wet and it will cause dark lines. Some brushes come with a wedged sharp handle that can be used to score the paper. A combination of applied paint, lifting, and splattering makes for an interesting painting.
The number one rule in watercolor: don't be too tight and try to control it. Be the director not the controller. Your piece will look static if you try to control it. I usually plan composition and values with a pencil thumbnail sketch. Making notes on light source, color and mood.
The number two rule in watercolor: learn how to use your paper and brushes at various wet stages. Too wet; the paint will bleed and the paint color will fade when dry.
( I know, I said the 'rule' word)
Here's one of mine that shows grass, splattering, lifting, and scoring.
Here's another. This one is worked a bit more and I used acrylic paint to splatter:
