Hey, Steve: Virtually every new kamado owner here on the forum has expressed frustration on how to acheive a low and slow fire on their kamados. Bottom line is it takes many burns to acheive the seasoning to get adequate air tightness in most all kamados. Here is a link with a great piece by Philpon on how to start a fire in your kamado for low and slow cooks. I know he is explaining based upon an Akorn Kamado. However, the same principles should apply for a KJ. I would encourage you to try his suggestions. Also, I would encourage you to try a real long low and slow, like a pork shoulder, for like about 8+ hours. During the cook, don't have overly high expectations. Set a goal of maintaining a long consistent temp of 300 degrees, or slightly less. After a few successes at 300 degrees, and as your cooker gets well seasoned, aim lower. For a brand new ceramic kamado, put in a good amount of lump charcoal, but only light about two or three pieces. place those two or three pieces on top of the unlit. wait for the temp to get up to about 150-170 degrees. Then, shut both vents almost all the way, just leave about a quarter inch crack on the bottom, the same, or less on top. It takes a lot of patience, but once you get it, it is very rewarding.
Good luck, Steve!