With my background blocked in, I work alla prima on the grasses. Alla Prima is Italian for "first attempt." For painting purposes, it defines the method of applying wet paint on top of wet paint rather than waiting for each layer to dry.
I find this method gives me a sense of freedom along with the ease of blending each stroke. My brushes are wiped with a paper towel often so a fresh clean stroke of paint can be applied, avoiding a muddy look.
Not all of the grass will be done this way. Once the birds are painted, I will go back into the grasses and add finishing touches. Some parts of the grasses (the darkest areas) may already be dry.