Again never having done this myself, but fwiw I know people who volunteer to do it for two big rides every year, so maybe it's not always an ugh job. And even if it is not fun, it is hugely important.

Another thing is when there are different ride distances to choose from, mark the mile numbers next to the arrows at any points where the routes go from running concurrently to splitting off. The last big ride I did just had different colored arrows but no numbers next to them, so I frequently wondered if I was following the right ones.

Good luck!