I've only had one experience with trying to register a homebuilt trailer. It was shockingly easy. You make an appointment to take it in to be inspected by the State Patrol. They slap a VIN on it and you give them a few bucks. I was in and out in probably 10 minutes and they didn't really check anything (lights or road-worthiness).

I suspect the easy/hard issue has everything to do with the actual State Patrol employee that is doing the check. If you catch them on a bad day, they could make it virtually impossible. Maybe I just got lucky?