I think people are underestimating McDaniel's intelligence.
I think he got sloppy when he panicked, but I think if he did this, knowing certain things about his personality from what I've heard from locals, he probably had all kinds of neat little tricks he researched to help get away with this kind of thing.
He was also a law school grad who had a very minimal social life.
He was into survivalism, which tends to go hand in hand with a meticulous researching of information that isn't practical everyday kind of stuff. My guess is he would be able to pull off a pretty clean crime if he put his mind to it, and a few prep classes wouldn't have precluded that.
I think if he did it, he could give the FBI lab a run for their money. I'm sure they'll find/have found some evidence, but I think if McD is the perp, he may have approached the dismemberment intelligently but I think he also suffered a period of decompensation as the stress built which lead him to make sloppy mistakes.
It's one thing to figure out how to dismember a body effectively without making a mess, but all the incidental things that come up after the crime aren't as easy to manage especially with stress and paranoia compounding. jmo.