By ground blind I presume you mean a pop-up tent style blind, I'm also presuming that this will be a gun hunt. Unless your blind is the low slung type that sets up over a pit like goose hunters use I wouldn't advise setting up in the cut corn field itself, you'll stick out like a sore thumb no matter how much you "brush in". When I hunt a field edge with a hardwoods border as you described I set up a few yards inside the tree line with a tangled background to conceal the outline of the blind. Brushing in is something I do only if I plan to stay all day, if your blind's pattern is compatible with it's back drop it shouldn't be necessary, although it doesn't hurt. It tends to be a noisy process, and difficult to do well in the dark.