knight504 said:
Even if you can't see chakra coils, shoving chakra into the opponent's body will probably always do some damage. It would just lack the accuracy of a Hyuuga practitioner.
It's probably a matter of effectiveness, too.
An example, using arbitrary numbers:
A: To hurt somebody's muscle by blinding charging on it with chakra, one would need, say, 10 units of chakra, and it would result in 5 damages(hurt, but still works).
B: With the Byakugan a Hyuga can hit the chakra pathway of the muscle, using 5 units of chakra, resulting in 12 damages(hurt a lot, functionality compromised, possible long-lasting damages)
C: A Hyuga with a strong enough Byakugan can even hit the chakra point of the muscle, using 2 units of chakra for a variable amounts of damages: at very least the muscle stops working for a while with no long-lasting effect, but depending on the chakra point it might cause rupture of the hit organ-
Bolt is probably Case A, but having much more chakra than the average Genin he can still be very effective.