How to learn to speak idiomatically?

Question

As a non-native speaker, I struggle a lot to come up with quick responses that sound idiomatic. It sucks because it also means it's harder to express some thoughts in fast-paced situations like meetings/chatrooms.

Anyone have advice on how to deal with this?

I am working on it by doing what I call "spaced reading": whenever I read a block of text that I understand, I look out the window and try to express that thought in my own words, peeking into the given text only if I'm stuck. (I've admittedly not been consistent so I don't know if it's been any effective.)

Answer 1

If you can afford to travel for an extended period, you could try total immersion. Otherwise, there are books, movies, television, podcasts. Maybe there are local language practice groups where you are that would let you participate in dialogs, such as those on meetup.com.
I find your idea above interesting, and I may try it for something I'm studying.

Answer 2

I would suggest the same ways that native speakers learn: books, television and talking to (other) native speakers. The more total your immersion, the faster you will learn.

For books and television, it should be material produced in English rather than translated or dubbed/subtitled, and it should be relatively recent. Closed captioning is useful so you can see as well as hear. The topic doesn’t matter, and I’d recommend using many different sources to get exposure to many different styles and situations.

For conversation, native speakers can give immediate feedback if you get something wrong, though most of us are too polite to do so unless you specifically ask. Likewise, most of us can’t explain why something “sounds wrong”, but we can at least give you an alternative that “sounds right”. Repeat that a few times to reinforce the pattern, and you can come here to ask for an explanation later.