You can learn it with training sessions outside of residency, and its going to be heavily dependent on the TMS machines you use in your job. You could have a ton of training on one in residency, and then be using a completely different one, and while the basics from a general knowledge standpoint will be the same, the practical knowledge of using the device will just not be there.
I agree that if you have access to it, you should at least get some exposure to it, but its not the end of the world if you don't. It really is straightforward so a little bit of operating knowledge and reading will be enough to get comfortable enough with it.