My paella pan has a porcelain coating, so I'm not much help with how to season yours.
I also had some concerns looking at the photo of it on an 18. Looks like the pan might choke out the air flow. I use mine on a 22 with a good pile of coals right in the middle and it gives really even heat.
...and I'm certainly not gonna tell the Chef how to cook, but a normal paella recipe relies on a fair bit of fat (from olive oil, and the chicken pieces that start the dish) along with a lot of water (or stock, if you're smart) to keep things from burning. And the end result is *supposed* to be a bit dry and crunchy, at least at the bottom of the pan. The art of it is to have your last dosing of stock coincide with the rice just finishing the cook, leaving a slightly dry pan for a nice crust on the bottom of the rice.
Good luck!