Getting an interview for global entry is actually pretty easy, you can just do it on the return leg of international travel with no appointment needed.
When you enter customs upon re-entry to the US there's a sign for a place where they'll do your interview real quick before letting you go. The downside (IIRC) is that you don't get your number for precheck either until you do this, so if you only do international travel 1-2 times per year you might want to find an interview time.
But, then again, I lucked out - TSA came to my work and did interviews there. Kind of weird but it got me in with little hassle.