Unless you need a serious bushog for the rest of you life for other use, I'd hire a forestry mulcher or rent a CAT skid steer with the drum style mulcher and get it done once, then you can maintain as you say.
Drum mulcher will blow though that stuff in one pass right at the ground and even the root crown, then you can spot treat and start mowing..... No sense doing any of this work by hand, or buying a new attachment (because a used one is going to give you fits) If you rent one, you can almost use it as a TILLER, and be sure you are getting the root crown. A contractor may not want to go to that depth.
I do a lot of selective clearing and grubbing with small equipment to build disc golf courses in wooded spaces, and I turn the flyways into natural walking paths. Dealing with the cleared material is a big part of the efforts, I don't want to pick it up and haul it, so mulching is best management practice. One machine. Not, Chainsaws, Grapple, Loader truck, haul to landfill, just so it can decompose there..... plus all the people involved. I don't own a Mulcher, as I can get the Government agency I am building this Disc Golf Park, natural walking trails, to contract that effort, but I still go in behind them and do some sawing and I use My skid steer to move the brush, trees, to a space where I reduce it so I can run my 4' bushog over it to reduce it to mulch and a stem.... See this 2 minute video to see my ASV RC 30 moving brush, and how dense the juvenile canopy is and the large Oaks, Hickory, Magnolia, Gum, that I leave/have to work around. And what it looks like after.... A year and a half later, this space sees 150 disc golfers and 100 walkers, mountain bikers and dog walkers using it...
Holland Park Build - YouTube