What men want is a woman who practices inactive listening. Despite common belief, active listening, where couples make an effort to listen to each other, isn't as effective as it seems. What's more effective is inactive listening, that is, listening to what the spouse is saying when he or she doesn't necessarily mean for it to be heard. I'm not advocating eavesdropping on your spouse, but whenever he says something out of the blue, it's probably because it's something he has to talk about. Here's how to practice inactive listening and what to do after your husband says something (hint: if you think you should question him about it, you're wrong. That could cause him to close up even more.).
Get him used to the idea of inactive listening. You should talk about it with your husband. Surprise him by saying something crazy like, "you know what? Those relationship self-help guides are all rubbish. As if we need help talking to each other. I reckon we're fine the way we are. In fact, let's just talk less to prove the experts wrong!"
Then simply talk. Even if he's not listening (or appearing to listen), talk. Let him get used to your "free talking", where you're basically rambling about something. Notice that this complaining or nagging. You could be doing something as simple as talking about your day and who you talked to, etc. If he wants to respond, he will.
After a while, he will also start doing the same thing. He will start talking about his day, what he did, who he met, he talked about. Do something else (cook, clean, lie on the couch) and absorb it. If you listen to him intently, that will unnerve him, making him less likely to practice this sort of talking.