I've machined a few custom gears for a race car many years ago. I tried a few things before getting a spur gear right. My opinion is that an actual gear hob on a mill and the blank in a chuck on a rotary table or indexing plate is the best way to do it. I've seen videos of people taking cuts manually with the carriage on a mill, but it looks like a full day job just to cut a single gear. Although the hobb was expensive, I was able to cut a 3" spur gear from alloy steel in about an hour. I don't remember exactly but I feel like they were made from 4130.
Hope that helps.