I recently unlocked the bootloader on my Nexus S, and I am looking at ways to finish rooting it. Every reference I find seems to be written assuming non-Google hardware, but the Nexus S is supposed to be open.
Your best source probably is Nexus S: All Things Root Guide -- which is a compilation/collection of several guides. Here you can probably pick your minimalist solution as well as go for the "big thing". In case you need some addional sources (easily to find with a simple Google search, by the way, as that is what I just did):
Don't get me wrong: I'm not saying you didn't search (your question clearly indicates you did). I put this just for reference by other interested readers here, who might need more details.