I find it easier to ask them for Scriptural support for their doctrines.
Reasoning From the Scripitures p. 283 - p. 284 Organization How can Jehovah’s visible organization in our day be identified?(1) It truly exalts Jehovah as the only true God, magnifying his name.—Matt. 4:10; John 17:3.
(2) It fully recognizes the vital role of Jesus Christ in Jehovah’s purpose—as the vindicator of Jehovah’s sovereignty, the Chief Agent of life, the head of the Christian congregation, the ruling Messianic King.—Rev. 19:11-13; 12:10; Acts 5:31; Eph. 1:22, 23.
(3) It adheres closely to God’s inspired Word, basing all its teachings and standards of conduct on the Bible.—2 Tim. 3:16, 17.
(4) It keeps separate from the world.—Jas. 1:27; 4:4.
(5) It maintains a high level of moral cleanness among its members, because Jehovah himself is holy.—1 Pet. 1:15, 16; 1 Cor. 5:9-13.
(6) It devotes its principal efforts to doing the work that the Bible foretold for our day, namely, the preaching of the good news of God’s Kingdom in all the world for a witness.—Matt. 24:14.
(7) Despite human imperfections, its members cultivate and produce the fruits of God’s spirit—love, joy, peace, long-suffering, kindness, goodness, faith, mildness, self-control—doing so to such a degree that it sets them apart from the world in general.—Gal. 5:22, 23; John 13:35.
Explain to them that you are having trouble with this one, since you aren't sure all the teachings are based on the Bible.
Ask them to Scripturally show why Jesus' disciples shouldn't talk to him or worship him. (John 14:13, 14; Acts 8:59; Revelation 22:20, 21; Hebrews 1:6 {see Kingdom Interlinear}; Revelation 5:11-14) Hint: there aren't any Scriptures saying that Jesus should not be worshipped, there are Scriptures showing that the angels worshipped him.
Ask them to Scripturally show that someone can be qualified to preach before baptism. There are no Scriptures to support this teaching.
Ask them to show where the Bible requires unbaptized people to regularly go to meetings, preach, have lengthy Bible study, answer questions to prove Bible knowledge,or pray a specific prayer of dedication in order to get baptized. There are no Scriptures to support any of this. (Acts 2:37-42; Acts 8:34-40; Acts 10:34-48 {less than 200 Greek words about Jesus and these Gentiles were baptized with Holy Spirit}; and Acts 16:14, 15, 25-34 {two separate accounts})
Ask them where the Bible says someone can get resurrected without figuratively eating the bread from heaven. (John 6:41-65)
Ask what religion the Bible says everyone should be and where it says we should worship. (John 4:19-26; 6:66-69; 1 Corinthians 3:16-23)
I would try this approach if I had it to do over again. It leaves the onus of defending indefensible doctrine on them, where it rightly belongs.
Respectfully,
AuldSoul