Of course, Zayn couldn't use the Soul Guidance technique immediately. He didn't have enough soul particles to exert Soul Guidance and blindly enter his Sparrow Spirits' body with his consciousness.
He had to come up with a proper plan to create his Spirits' Soulrings as quickly as possible, otherwise, the exponentially increasing consumption of soul particles would drain him dry in no time. He wanted to avoid complications if possible. Thus, the Sparrow Spirits would have to be overflowing with soul particles which was not yet the case.
They didn't even possess enough soul particles to create a stabilized soulframe, which was actually what Zayn wanted to help with since it was much faster than creating the whole Soulring in a single session.
He knew that it would take a while before he could use the Soul Guidance technique to help his Sparrow Spirits but it was not as if time was running away from him.