This is what I don't understand. My thoughts become too complicated. Like he hired a hit man. We may think he's stupid, but not that much. He probably did hire a hitman. The hitman did it in the garage. Took the body with him and the body is long gone in a professional NYC kind of way. Only one thing, he made a mess. She probably fought back. So there was some cleaning to do. That was left to FD. He used old clothes and sponges. Put them in bags, loaded them in his truck. Washed up in the kitchen. Called MT. Said, hey, do you want to take a ride with me. I've got to do a trash dump. This probably isn't all that weird. He's probably done it before to avoid having to pay a trash company to pick it up.
Now the problem with this is, he would have had to be at JD's house. Do we know that? Other than his DNA in the kitchen, is there any evidence he was there? LE probably knows the answer to that question and is one reason they wanted all the surveillance video. Also, if there was a hitman, there would probably be some video evidence of that. Except I would think a good hitman would know how to avoid being seen. I also think FD probably knew a way to sneak up on the house without being seen. But if the body left with the hitman, I don't see how he could drive away with the body without a chance of being seen.
To get rid of the couple (maybe just one) bags of rags, he loaded them into her car and drove it to the park. Maybe that's where his truck was anyway. So, he got to the park, moved over the bag of rags and left.
So things I would be checking for (which LE probably is) is money transfers, or more likely crypto exchange accounts. If he was planning it a long long time, maybe he funded it by trickling money into it. Probably wouldn't be detectable. He probably bought the crypto currency anonymously in Greece.
Which all means, there probably was nothing at the incinerator. Probably all there was were the rags. They're not going to find a body in a lake. He didn't cut her up. It would have been perfect if it had been cleaner. He screwed up a little bit in dumping the rags. Will it be enough?