“I find it hard to reconcile these two sentences. How can you possibly convert someone to Christianity while hiding the fact that you believe in Christ?”
Subtlety.
The most impressive way I’ve seen is they move into a Orthodox Jewish neighborhood, live there, work there, go to synagogue there. Sometimes for months or years. Then volunteer at synagogue for whatever. Do a fine job.
Then, after a long while, start sharing their views. There was a recent exposure of this by a couple in NY. When exposed, they moved to Chicago and started over.
This also happens in Israel a fair amount.
The more common approach is the “Jews for Jesus” approach that shows up on college campuses and pretends to be Jewish, until they make their spiel.
RE: pretends to be Jewish, until they make their spiel.
They would pretend to be Jewish if they are NOT indeed born Jewish. But are they?
What you seem to be saying is this — No Jewish born person who accepts Jesus as the Messiah is truly Jewish.