Only a few. Some were confused on the Baptism of Repentance (as administered by John the Baptist) and the Baptism for Membership in Christ's New Church (which came later in the three year ministry and post-resurrection). Some Jewish converts needed to be taught that circumcision was no longer required in the New Church.
The difference between the two baptism was the ordinance for Confirmation for the Gift of the Holy Ghost.
Cleopas and Simon were on the road to Emmaus discussing the events of the Crucifixion when they were joined by the veiled Christ. So what does Jesus do for these two men? He teaches them all over again: "Beginning at Moses and all the Prophets, He expounded to them in all the Scriptures the things concerning Himself" (Luke 24:27). At eventide, after the Savior disappears from them, they rushed back to Jerusalem to share their experience with the Apostles. There Jesus appears to the whole group fully revealing Himself.
This was the SOLID core of Christianity at the very beginning. That included faithful women who were witnesses of the Resurrection. Plus all the devoted disciples from the three year ministry.
There was solid orthodoxy at the beginning. It was decades later when the Apostles (Peter and Paul and others) were warning of devious wolves in sheep clothing.