I'm have no SARS experience, let me say that right up front.
I do have some experience bushwhacking - lots of it. The type of forest is black spruce, willow, alder and dead fall - and all of it dense. Something like this:

A poncho does not work. It is forever getting caught on branches and schrubs. I also find that my use of arms is somewhat limited compared to a rain jacket. I'm moving branches, steping over logs, crawling under logs, all of which require the use of my arms for balance etc.
The only type of clothing that works for me off trail is a good quality Rip Stop Nylon rain suit, gaiters, and a rain hat. I also always carry Mcnett Tenacious Tape and a needle and thread.
Good for you to be thinking of volunteering.