The real trick to making making your grass look real is to understand how the brushes work. You're gonna kick yourself when you see how easy it really is!
Grass for daytime
scenes
1: This explanation won't be as detailed, because the steps are
essentially the same as before, except this time, you should have a white
background, and background color selected on your palette. Once
again, run the single-blade grass brush followed by the triple-blade
brush over the very bottom of the canvas. You have to run the brush over
a few more times than you do for the nighttime look in order to make it
look fuller. Also, don't limit yourself to green and white combinations,
use green and >cream as well as green and mint
combinations, to make it look more natural.
2: You're primarily going to want to use the single-blade brush for daytime grass because the colors it blends better. Repeat the same gradual shrinking process as you did for the nighttime grass, making sure to vary your color combinations from time to time.
3: Now, set your bottom-most layer's opacity to 50%. I think this gives it a more "off in the distance" kind of look to the grass. Also, using the burn tool selected to a range of midtones and an exposure of 50% go over random pieces of grass on each layer. This helps to break the monotony of the colors by make richer and darker shades of green. If you lower the layer opacity at all, make sure it's not less than 90%.
4: As for finishing touches, make sure you don't leave the background white! Go for a light blue, or other sky color. Also, with a >yellow scattered brush, make sure you add little things to the grass, to give it that lively look!
