Right... God is good though, so if you ask him for his spirit he will fill you with it and you can be sealed after, after you believe on his name (Jesus').
Ephesians 4:30
And do not grieve the Holy Spirit of God, by whom you were sealed for the day of redemption.
1 Thessalonians 5:19
Do not quench the Spirit.
To ask God now for the Spirit is an insult to His working in us. You are effectively saying He did not do what He promised He would when we believed on the Lord Jesus. You don't ask for a gift, it is given freely.
Acts 2:38
Then Peter said to them, “Repent, and let every one of you be baptized in the name of Jesus Christ for the remission of sins; and you shall receive the gift of the Holy Spirit.