I used a full tri-suit (with vest top half) for my last ultra as it was very very wet/windy, and running through rugged terrain with brambles,ferns etc.
I focused on having a decent training routine - I've always been an avid runner, so I just upped my weekly mileage up to about 65mile which wasn't much as I did half-maras each day, then did 2/3 18hrs sessions per week 8 weeks beforehand. I used to jump on the treadmill on max incline @ ~6-10kmph with a 15kg weighted vest on + full camelback to get used to carrying the weight.
I did the Ramsay's round, which is a ultra - but over a 24 hour period as the terrain is mountainous (the elevation gain at the end was over 28,500ft).
What I found out from longer 18 hour sessions is that I got really bored of the food, and felt i couldnt eat anymore - although I needed to keep the carbs/h20/salts coming in every, 20-25mins. I did this by mixing savories and sweets up, different contrasts in food made it easier(ish) to take in.
Be sure to have a hard, but enjoyable training routine in order and work through it, I gave myself 2 weeks off before that ultra for some decent rest.