Those under grace only teach sinners, not others under grace

Eph 3:16-20 specifically states that it refers to saints , those who no longer continue in sin...

There is no 'How to' about the covenant of grace, rather read it and see [Heb 8:8-13] that it is unconditional upon the few [Matt 7:14, Rev 7:3-8] who are sealed into all truth by the holy spirit of God Himself [John 16:13] so to become saints in THIS lifetime as the GIFT of God, not something on does or takes or can engineer :-

Ephesians 2:8 For by grace are ye saved through faith; and that not of yourselves: it is the gift of God:

Simply read Paul for confirmation of Exodus 19:6, that the saints of this lifetime are predestinated by promise of God from the holy nations , the House of Israel and the House of Judah :-

Ephesians 1:5 Having predestinated us unto the adoption of children by Jesus Christ to himself, according to the good pleasure of his will,

6 To the praise of the glory of his grace, wherein he hath made us accepted in the beloved.
7 In whom we have redemption through his blood, the forgiveness of sins, according to the riches of his grace;
8 Wherein he hath abounded toward us in all wisdom and prudence;
9 Having made known unto us the mystery of his will, according to his good pleasure which he hath purposed in himself:
10 That in the dispensation of the fulness of times he might gather together in one all things in Christ, both which are in heaven, and which are on earth; even in him:

The royal priesthood being assembled first, God requires but the few whom he has given to Jesus now to prepare for the gathering together of all in one in the kingdom...

This why Jesus said he has come first only for the House of Israel [scattered long before the Jews , amongst all nations] :-

Matthew 15:24 But he answered and said, I am not sent but unto the lost sheep of the House of Israel.

most folks don't even read the OT to find out who te House of Israel were and their role in Christianity alongside the Jews [who also do not recognise this vanished nation although their own holy writings describe the role at length]

If you listen to sinners teaching you how to extract grace, rather than scripture which says it is given to whom God says He will give it, then that is your own affair... but Jesus has said that he will not take anyone who has not stopped sinning and you will find he is very serious about what he has said :-

Matthew 7:23 And then will I profess unto them, I never knew you: depart from me, ye that work iniquity.

Luke 13:27 But he shall say, I tell you, I know you not whence ye are; depart from me, all ye workers of iniquity.

2 Timothy 2:19 Nevertheless the foundation of God standeth sure, having this seal, The Lord knoweth them that are his. And, Let every one that nameth the name of Christ depart from iniquity.

The fact is that God NEVER sanctioned sinners to teach anyone in his place , even the saints are only entrusted with teahing the truth about the Messiah [Christ] who will rule a re-united Israel in the kingdom of God , as promised by God but ignored by modern sinners in divided 'chrsitianity' of countless creedal beliefs and private interpretations of scripture [denounced by the saints of scripture]

The covenant of grace itself states:

Hebrews 8:10 For this is the covenant that I will make with the House of Israel after those days, saith the Lord; I will put my laws into their mind, and write them in their hearts:

11 And they shall not teach every man his neighbour, and every man his brother, saying, Know the Lord: for all shall know me, from the least to the greatest.

John 6:45 It is written in the prophets, And they shall be all taught of God. Every man therefore that hath heard, and hath learned of the Father, cometh unto me.

1 Thessalonians 4:9 But as touching brotherly love ye need not that I write unto you: for ye yourselves are taught of God to love one another.