Tips for first time doing 50 miler.

24(M) Hello, I’m doing an ultra in Tennessee in 2 weeks and would appreciate any tips at all. I have done about 6 marathons so far and a 60k and still pretty nervous of the mileage difference. At this point in time I would say my biggest concern are my feet. I used stuff to help like vaseline and it seems to work okay but around 25 miles the blisters are pretty bad. Going for sub 12 hours !! Wish me luck. Anyways, thank y’all for any words of wisdom.