I can’t speak from personal experience as I haven’t contributed to Rust yet, but according to the org revamp rustup falls under the Dev Tools working group and it looks like that’s headed up by @nrc (or @aturon).
Other team members can be found on the Community’s Rust Team page.
One of the goals on the 2018 Roadmap is to invest in mentoring and developing mentorship relationships so I’m sure they’ll be able to provide guidance in some way.