The proper answer to Aaron's question is: Queen City Cycling hosts practice sessions - or just plain practices, on Tuesday and Thursday nights at 6pm at Elmwood Park. All Cx-urious people are welcome to come and be introduced to the sport. There is a course set up with barriers and everything and being shown the course is quite helpful.
Here is my introverted, socially awkward accounting of what I did to feel ready, which is to say, I'm not normally at Elmwood on Tuesday or Thursday nights.
Not withstanding the best season of riding I've probably ever had and some experience with MTB racing...
1. I purchased a Cx bike.
2. I took the GPS map of the Elmwood course to the park and tried to make my way around according to that - with marginal success. Nevertheless, riding around in any grass weaving around any trees is a very good place to start.
3. I let time pass - now the Elmwood course is more worn in and is easier to follow. Some parts remain ambiguous without a guide. I'm willing to show the course as I and my son have discerned it - I'll be your guide. The actual designers of the course can likely be found on Tuesday and/or Thursday nights.
4. I went around the course at Elmwood a few times on a few different days, sometimes with The Boy 17, generally stopping completely at each barrier before stepping over.
5. The Boy 17 passed me this GCN video about how to dismount - https://youtu.be/qdRyXQN90Kc - and I watched it.
6. I watched the GCN video about how to remount - because you gotta get back on too.
7. I went back and forth across a marching band field with The Boy 17 for an hour dismounting and remounting and lifting my bike. We sort of raced but mostly just tried to push each other a bit to keep speed.
8. I went to Elmwood Park and did 10 laps of competitor free race simulation, including proper (as best I could) navigation of the barriers. With this I have an hour baseline of lap times which I can try to improve upon. Some context - I think my selected race categories are 30 minute and 20 minute races.
9. I purchased a proper cycling kit - because everything needs to stay in place for all the remounts.
10. I bought a USA Cycling License and registered for the race.