It's not easy, and no, it doesn't work every time. Plenty of people who see their material conditions improve do not become socialists (or even properly credit whoever caused their improved conditions), just like plenty of people who see their material conditions deteriorate do not become socialists. You have apolitical folks and reactionaries at all economic strata. Material conditions play a large part in people's political beliefs, but framing things in political terms and convincing them your politics are right plays an enormous role, too.