here's the course. The place where I dropped my chain is around 6 minutes. Of course these guys just rode up it LOL. I only had one practice lap and didn't realize there was a line (or if I could ride it :P). The wood chip parts are under the barns. These guys did fine, although you see one guy put a foot down. There's a different video where you see a guy wipe out.
So I took some time to watch this and here's what I can offer
A lot of these riders look like they can't turn well on dirt or gras, some really bad and tight angles. It looks like a lot riders getting by purely on power. Even in those wood chip sections they're just staying up for being able to balance. The one rider right at the start that just takes a really douche line (sorry if this is you) by cutting on the inside for a turn. The guy was squirrly as all hell
as for that wood chip section the best advice I can offer is just get comfortablr with some rear wheel slide and learn to turn your hips through those turns. These two things go hand in hand but tight turns like that are more about pushing through the turn with some counter balance and hip wigglin
if you know of any sand pits near you just go practice doing figure 8s in them. I'm serious, Jeremy powers recommends this in his video stuff.