It was pretty much just two pitches. He had a 98 mph-ish rising fastball that he would use to walk hitters up the ladder until they were swinging at pitches at eye level. And he had a kneebuckling 12-to-6 curve that he could throw for strikes. It was almost unfair when coupled with the fastball.
The Mets helped screw him up too, as I remember. They decided after 1985 that he was throwing too many pitches (true), so they thought the best way to handle it wasn't to just take him out of games earlier, but to have him try to pitch to contact more and stop striking so many guys out. It didn't work out too well. Then he got arm trouble, and then he had a lot of free time while he was hurt, which he filled up with a drug habit, and that was pretty much it for Dwight Gooden. A giant shame, even if he was a Met.