One Marathon to Ultra Trail 50k in a Month HELP!

I ran the Pittsburgh Marathon in May (2018) and plan to run a 50k in Michigan called the Two Hearted.

I used the Hanson Method for the Marathon.

What training or plan should I use with a 5 week turn around?

I ran Chicago in Oct. Then took a break from road marathons. I was just DONE. I got roped into a 50K having only 10-11 miles per week. At that point I was just doing maint. and trying to not get fat. I had 8 weeks until showtime. I jumped from 10 miles per week, to about 17-20 the next. I did not really use the 10% rule for mileage due to time crunch. I trained on the trails that event took place. My longest single run was 20 on a Saturday, then 13 on a Sunday in order to prepare myself on tired legs. I was doing strength training 2-3 times per week. I did not do hill repeats or any tempo as it is trail, and as far as I was concerned, it was not about time with a 50K. It is about completion. So time on my feet was my focus. I am not an expert runner by any means.

Yes, making a big jump in distance in a short time is going to be about just finishing. Getting time on feet would be important -- not speed, but just practice being out there for a long time. It would be easy to overdo it and get injured when trying to cram in fitness during a short time. For ultras, I'd probably recommend just really long hikes (even all-day hikes) in the kind of terrain you'd be in. That way it's low-impact and easy recovery but you get the tiredness and time on feet.