I've been off-line for a while so I don't have much offhand knowledge of your past posts -- but what type of machining equipment do you have access to?
I've seen the 80/20 receivers done in minimally-equipped home shops (e.g., not much more than a drill press, vise and some files), and the finished firearm worked just fine. Rough as cob, but worked fine! But I have also seen small issues that completely frag the project, such as the buffer tube not being concentric and/or axial to the upper receiver, preventing the BCG from cycling. That type of thing is usually discovered only after the guy has like 120 man-hours into it. Losing a $250 lower hurts, but to me, losing the time hurts even more!
If you get an 80% lower that already has the mag well broached, finishing the rest on a milling machine is done with basic techniques. There is some tooling specific to the AR lower, but limited to things like extra-long drills and reamers that are not standard fractional sizes.
I have completed a few of these lowers over the years and I always plan the project through before cutting. The "plan" is basically a listing of the operations and the order they need to be completed in, in order to minimize the number of setups that have to be done. (Each setup is an opportunity to introduce error.) I constantly check my work throughout the machining process to make sure the parts haven't shifted, etc.
Producing the plan, doing the machining, test fits and all work takes me about 20-25 hours, plus one to three hours for metal finish. Most of the work is on the mill, but for the buffer tube hole, I prefer to mount the receiver on the lathe and single-point thread it.
BTW, the Ares lower looks like a pretty standard, happy forging. It should be a fine basis for your project.
