My "trick" is to use tiles, but
- with several variants, 4+ different tiles
- small enough tiles that there aren't big distinct shapes of grass within the tile that will be noticeable when repeated
- with different edges that line up to form different grass clump shapes when put together (this too benefits from smaller tiles)
Towards the end (after placing any props and such, which will cover up a lot of the tiling), the remaining bits where tiling is still noticeable can be touched up manually.
This is the method I'd employ for almost all terrains, tbh - grass, dirt, water, bricks, as well as transitions.
It's a lot easier to avoid the "tiled" look with tiles than it is to manually obtain a good level of polish on an un-tiled expanse like this. The key thing to avoid the appearance of a grid, rather than avoid tiles entirely. Break up those blocky straight transitions, and use a good set of variant tiles, and most people won't even notice you're using tiles at all.
In addition: you can embrace solid areas of colour. Your grass right now, completely solid green, actually looks pretty good, just a little boring! Solid colours "tile" perfectly, don't look tiled, and are easy to draw. All you need to do to keep the image from being boring is to break up the negative space with just enough unique elements and props that the scene doesn't look empty, you don't have to fill it all with texture.
