I'm in a similar situation in upstate NY as you are in WI and was doing about as you are, taking downed, standing dead (carefully), and obviously diseased trees for firewood. On 60 acres (about the same as my wooded land), there's more than enough of that kind of stuff, unless you're burning a lot more wood than I am (about 5 full cords per year). I had a state forester walk through with me and point out some obvious truths that helped me a lot in going beyond just cleaning up. Once cleanup of accessible downed, diseased, and standing dead logs was well along, I focused on the really crooked trees that will never have value for sawlogs. Lately, I've been taking the multi-trunk trees (mostly red oaks), unless they're not at all crowded. They tend to rot out from the inside because they are often second growth from sprouts of previous cuts, and the remains of the old stump that are enveloped by the new growth eventually rot and that spreads to the growing trees eventually. After that, I look at crowding. Some crowding is good for younger trees to stimulate straight growth, but once they begin to want to crown out, I try to thin a little to free the remaining trees to prosper by increasing the ground moisture and nutrients available to those that remain. Generally, I'll try to have 20' or more between trees of greater than 10" dbh, although that's probably also a little crowded. I found that I can't use enough firewood to accomplish all of the above, and I've been at it for more than 30 years. This past year, I did give some of the multi-trunk oaks to a young neighbor who needed timbers for a post and beam barn that he's building. We got plenty timbers for him from by reducing the crowding on only a couple of acres of my woodlots. By the way, a lot of brush means that you're a ways from reaching what they call a "climax forest". In that situation, the crowns are so thick that brush tends to die out, and young replacement trees only do well where a mature tree or trees are removed to allow sunlight through. I've also read that it's desirable to let 4-6 dead trees stand per acre to serve as habitat for various critters, birds, and desirable insects. I tend to let fewer than that remain where it's easy to get at, but more where access is more difficult, so I guess it averages out.