Preen is a seed germination inhibitor and will only affect seeds. Brush (which I assume is a woody plant growth) is likely sprouting back from any roots you left behind and Preen will not affect that. You can instead paint a little Brush-Be-Gone on brush stumps to try and control regrowth.

I would certainly use a product like Brush-Be-Gone on any invasive shrub growth, and I might also do a one-time application of Preen followed by a heavy layer of pine-needle or leaf mulch.
Also, this might sound like a silly tip, but to avoid weed growth in wooded areas, don't rake the leaves- not in the fall, not in the spring, not ever. My father made that mistake a few years ago- now he has poison ivy galore. The leaf cover prevents many unwanted plants from growing. Removing this natural mulch is essentially a disturbance event which allows exotic invasives and other aggressive plants to take hold.

Dirt uncovered is a potential home for any seed that comes along. You can plant things you like, let leaves mulch it, but the ground wants something on it. Maybe some understory bushes that flower? Woodland plants that are attractive to you, something to keep the dirt busy. My woods plants seem to grow in waves. Early stuff comes and goes away. Then something else comes up, then later plants. Some I like, others are pesty. I sure wouldn't want just bare ground all year, not good for the land, erosion would be easy in my area with sluicing rains. Rain washes away leaf cover sometimes.
Preen will only work for a bit, needs to be applied before any growth. Weed-b-Gone sprayed, leaves a residue that may leach into surrounding areas, the watershed with rain runoff.

Corn Gluten is getting good reviews as a natural inhibitor of green growth. Just sprinkled around, it is supposed to prevent plants, doesn't do damage to other areas or runoff. Might be worth checking. Straight cider vinegar worked well sprayed on some broad leaf weeds I had, really did them in. Didn't touch some other weeds right beside them. Another maybe for you.

Maybe you should re-evalulate how you're mantaining the woodland border.Establishing a succession of planting heights to gradually merge the woods to the lawn might make maintanence a little easier.From the trees to the understory trees,then bushes and shrubs, perrenials,and finally the lawn,if you have a lawn.A naturally grown in woodland edge is a beautiful site.Take a naturally occurring example such as a wooded lakeshore or a roadside as a models for your own property.Remember a successful garden design is one that doesnt look designed or gardened