In my case I corrected a slight bat effect by using three exercises:
1) Reverse trap jelq. (This may go by any number of names.) When erect, trap at the base using a regular o-grip and kegel to fill up properly. Then grip with the other hand just below the glans and do a dry jelqing motion towards the base. Make sure that you keep the trap (tourniquet) in place to avoid outflow of blood.
2) Slammers. Don't know why since the mechanics of this one make it seem like it would increase the bat effect but it worked for me.
3) Constriction. With a cockring (elastic and adjustable, never anything else) or a cable clamp you can work such a large part of the shaft and place added emphasis on the area you really need to work. I really only do the basic constriction (slap it on, stay hard, enjoy the sight).