You brother seems to think God is limited as to what He can do and share with a finite man. The scriptures tell us if we have faith the size of a mustard seed we can move mountains. Point is, just as scripture tells us, with God nothing is impossible. Simple answer it is through the same power and authority by which finite men raised the dead, walked on water, healed the lame, knew the future etc…
We see in scripture angels and elders in heaven, as go betweens, offering up the prayers of saints on earth. Scripture clearly shows some prayers from saints on earth pass between the saints and angels in heaven through the Lamb=Christ to God.
[Rv5:6 And I beheld, and, lo, in the midst of the throne and of the four beasts, and in the midst of the elders, stood a Lamb as it had been slain, having seven horns and seven eyes, which are the seven Spirits of God sent forth into all the earth. 7 … 8 When He had taken the book, the four living creatures and the twenty-four elders fell down before the Lamb, each one holding a harp and golden bowls full of incense, which are the prayers of the saints .]
[Rv 8:3 And another angel came and stood at the altar, having a golden censer; and there was given unto him much incense, that he should Offer it with the prayers of the saints upon the golden altar which was before the throne. 4 And the smoke of the incense, which came with the prayers of the saints, ascended up before God out of the angel’s Hand .]
[Mt18:10 Take heed that ye despise not one of these little ones for I say unto you That in heaven their angels do always behold the face of my Father which is in heaven. ]
Jesus says their angels behold the face of his Father. The angels stand in the presence of God. They have continual access to the Father. If one of their little ones are in need the angel serves as the child’s intercessor before God, otherwise what’s the point?
[Lk15:7 I say unto you, that likewise joy shall be in heaven over one sinner that repenteth , more than over ninety and nine just persons, which need no repentance. 8 … 9 … 10 Likewise, I say unto you, there is joy in the presence of the angels of God over one sinner that repenteth.]
Who rejoices in the presents of the angels? Saints in heaven. They know when a sinner repents and rejoice in the presence of the angels they know what is going on and pray for us. We are a people, a body not just lone individuals. It’s not Jesus and me but Jesus and us. The entire body of Christ, through which the Spirit flows in union with that body we all receive the grace to persevere.