It depends on how high the level of kido is and how strong the user is.All Kido probably have an incantation. But strong in Kidou characters can cast Kidou without incantation in order to save time. You can but they are weaker to my knowledge.Yes, all Kido has an incantation. In battle, many will not use the incantation to fire the attack immediately at the cost of some of its power. Most recently, Aizen used the incantation for Hado 90 which he had used earlier in the series without the incantation