I don't even know if I'm asking correctly, but you know how you kinda have to just draw on ground covers and they can look messy if you aren't very precise? Is there anything that can help with making perfect shapes with them? I've never been much of an artist, haha.

I use short fencing to outline areas if I'm trying for straight lines. You could use these modular flowerbeds to do the same thing (since there's a round one) - http://www.modthesims.info/d/158602

The short fencing was a good idea, thanks! I'm giving up on a perfectly round driveway for now.

If you're doing ground cover in straight lines, the easiest thing to do is outline the area you want with floor tiles and then spray. This allows for straight lines since the ground cover will not spray on floor tiles, only exposed ground. Round either takes a steady hand or as mustluvcatz suggests, a piece of cc. If you spray in one spot though, keeping very still, you do get a circle the size of the brush.