We should all work on that every chance we get.
You have two things going on here at once, there is being born again which is salvation and there is the baptism of the Holy Spirit which equips for service. In the days of Moses the 70 elders where baptized in the Holy Spirit:
Then the Lord came down in a cloud, and spake unto him, and took of the Spirit that was upon him, and put it upon the seventy Ancient men: and when the Spirit rested upon them, then they prophesied, and did not cease. (Numbers 11:25)
Then there were Bezalel and Aholiab:
Whom I have filled with the Spirit of God, in wisdom, and in understanding, and in knowledge, and in all workmanship: (Exodus 31:3)
Salvation on the other hand is when the Holy Spirit makes us a new creature in Christ:
In whom also ye have trusted, after that ye heard the word of truth, even the Gospel of your salvation, wherein also after that ye believed, ye were sealed with the holy Spirit of promise, (Ephesians 1:13)
We can't really know what went on in the heart of believers in the Old Testament. We do know that true repentance and saving faith only come through the washing and renewing and regeneration of the Holy Spirit. We know they received the word, some fell away and never came to saving faith, some responded in faith and bore fruit. The key here is saving faith and we have plenty of examples of that from the OT.
Concerning this salvation, the prophets, who foretold the grace that would come to you, searched and investigated carefully, trying to determine the time and setting to which the Spirit of Christ in them was pointing when He predicted the sufferings of Christ and the glories to follow. (1 Peter 1:10-11)
Notice the Spirit was in them. The revelation was greatly expanded in the New Testament witness, there is no question about that. But the sanctification of the Holy Spirit with regards to salvation came through in the OT as faith and repentance. True faith and repentance, righteousness and sanctification have always been a work of the Holy Spirit in the heart of the believer. They may not have called it being born again but the essential process remains unchanged, righteousness is by grace through faith. The righteousness of God in Christ can come only from God since it's based on his divine attributes. Producing those qualities in the heart of the believer is the sole responsibility of the Holy Spirit, always has been.
Grace and peace,
Mark