Update...
It was just getting toooo crazy and I ended up having it cut. Trimmed, to be more accurate. I found a coolish little salon in town that was very highly rated - nothing fancy, just a few steps above Hair Cuttery. I explained exactly what was going on (early stages of MtF transition, want to grow hair out but it's just too unruly and scruffy at present, don't cut anything off the top, etc.) She was extremely understanding, trimmed only the teeniest little bit off the ends to smarten it up, and gave me a good education in how to care for it and style it during this awkward stage. I'll definitely be going back to her once it gets out of control again.
It looks far better now, even though it's probably been trimmed no more than 1/4" (half a month's growth?) Cost me $30 because it was still considered a guy's haircut. Literally the first time I've ever spent money on a haircut I've been happy with.