The fundamentalist christian mind isn’t materialistic, it’s dualistic and has an inverse spirituality.
If it’s Yehuborim = God/good side
If it’s non-Yehuborim = Satan/evil side
“Yehuborim” here just means the literal, surface bible and then the added xian doctrine after. The deeper doctrines of the Yehuborim are labelled as “satanic” by xians.
They’ve been trained to look at religion in an inverted way. They’ll deny that even Yehuborim are Yehuborim and are actually “pagan”, using the stolen techniques and practices of the Yehuborim as proof that they’re “pagan”.
It’s quite insidious to understand what it turned them into. Paganism and any non-xian religion (and even xian sects they don’t agree with) are all “Satan’s kingdom”. It reinforces a solipsistic “us against the world” narrative. If you ain't in the group you're automatically part of "Satan's kingdom".
Faith is strongly empathised as anything said or done against the religion is “Satanic lies” trying to condemn their soul by getting them to abandon the religion. Emotion and ego play strong roles here. Attacking them would only strengthen those feelings as that “validates” their beliefs.
To change that requires an emotional trigger that this all may be wrong. That will differ depending on the person. Ultimately you'd have to show them that the religion they currently hold is actually counter to the deeper values they hold (morality, truth). They associate their religion with ultimate truth and goodness. For some reading the parts where earth is 6000 years old or where yahweh killed and ordered others to kill innocents, including children, is more than enough. It was for me. Others though will try to justify this with phrases like "God can't do no wrong" "Bible can't ever be false", until ultimately the book itself is the "utlimate good and truth". I don't think we can convince those who have merged truth/goodness with the bible itself as that requires one to reject their inner moral compass and what their own eyes can verify for them in favour of what the bible says. They'd have to dig themselves out of the hole they got into if they actually merged the bible with truth/goodness in their mind/soul.
This is something xians and leftists have in common, rejection of goodness and reality for something twisted that wants to appear as such but only exists in the false abstract rather than in any genuine way. This all applies to muslims and other kinds of abrahamics too, or any Yehubor-made ideology. The book is the end all for truth/morality since the book = God's command. Reality and common sense is rejected in favour of pseudo-reality and pseudo-morality where the only criteria is if the book says so. With atheist materialism it's at least partly grounded in reality since they use logic/morality to see through the bible's lies, but usually have a blindspot for leftist bullshit, and vice versa for xians who see through leftism but not the bible. Blind vs deaf.
To say prayer doesn't work isn't really accurate. A xian with a powerful aura or a group of xians praying can definently have an effect. You can use prayer as an example to show the power one can have in using the Divine energies.