Ask HN: How long did it take you until you became “fluent” in TDD?

I've recently gotten an offer for a project where I can pretty much dictate the setup. For my own professional development, I always try to add a new aspect to each project.

This time I'm aiming for 100% code coverage and an app written with TDD methodology.

The process is sooooo slow though. I'm guessing it will speed up after a while, but as it is, I feel I'm losing lots of hours for small gains.

For those of you that always TDD, how long did it take you until you felt that it wasn't holding you back in delivering?