Try not to focus entirely on the jab. If you try to apply technique to the hand or wrist, it will not work. I've seen kotegaeshi applied to a very fast jab, when the instructor moved in on the side, began by putting the back of his hand on the attacker's shoulder and sliding down to the wrist. He said that if he started at the forearm or wrist he would miss.
Also, balance taking or kuzushi, is more important than applying specific technique. If you can enter deeply and turn, you will have a variety of techniques to apply, but kuzushi after entering is most important.