Pulse Shaping

Pulse Shaping is a passive form of Chakra Flow and the complete forgoing of using Hand Seals when using chakra-related techniques. With his Eternal Mangekyō Sharingan, the Nara focused his creative mind inwards towards his own Chakra Pathway System. Studying how his chakra moved and felt, he used his ocular prowess to mimic how his chakra moved when performing each of the twelve zodiac signs.

The initial process required multiple clones in order to complete. Doing this inexplicably increased his Chakra Control to near masterful levels, eventually reaching the master level of control upon completion.

Upon his initial completion, he had to relearn the techniques he knew so far to employ the new style of Chakra Flow. Without the use for hand seals and the sheer flexibility of his chakra, the speed at which he can perform techniques allowed him the luxury of using even the strongest techniques in a near instance.

After a while of struggle, he would eventually complete the process of using two techniques at once without the use of a single hand seal. Because of this, his level of chakra control soon became one of the best in the realm.

Trivia
Certain other shinobi/kunoichi are capable of using their own techniques without the use of hand seals. Whether this is related to Pulse Shaping or something else entirely, is bound to be different between each of them.