In my case: slowly.
It helped that I initiated D-Day, and didn't do it right away when I found the first IM conversation between my wife and her AP. I waited a bit, gathered as much information as I could, and only acted because I knew they were planning another rendezvous the next morning. I didn't think I could hold it together through the night knowing that was going on the next morning. But I still knew what had happened, more or less when it had happened, and who was involved. Then I didn't tell her I knew that, I just said "Hey Mrs. ascian, I saw an IM between you and AP and it's got me a little worried."
She spilled everything, without further prompting from me. She was honest about her dishonesty before and didn't try to spare herself or blame me. Right away that laid a foundation that we could build trust back on.
And then it was monitoring. Almost constant monitoring of her cell-phone activity, her FB and Google accounts, digging through her (still unlocked) computer at home when I was worried. And she let me, she understood that was what I needed. If there was something that worried me, we talked about it. If my day (emotionally) went to crap, we talked. If her day went to crap emotionally, we talked.
Because of my wife's nature, one of the things I did that helped her be comfortable with my level of access was to offer her almost the same with just a couple caveats. The only two accounts she doesn't currently have full access to are the online journal that I use to organize my thoughts about my emotions and such since the affair, and my SI account. She knows she's welcome to see either of those, but I've asked that she do it when I'm around since there are some raw and hurtful thoughts put down in those areas and I don't want her to stew on that for hours before we can talk about it.
(And if she hadn't come completely clean, I'd have pretended to buy it and gotten everything in order to ensure I had primary custody of the kids in the divorce.)