[thingification]

There are games out there that help you learn the skill of switching quickly.

As at least one other person has commented, context acts as a switch even when you can't directly "find" the switch consciously. It isn't only the keyboard. I learned colemak on one keyboard while I continued with QWERTY on another, and it wasn't a big surprise that it was hard to do the reverse for a while. What did really surprise me was that I couldn't type QWERTY in the typing drill software I was using for Colemak, and I couldn't type Colemak in the online typing test where I was used to typing QWERTY! It wasn't a subtle effect, quite a dramatic speed plummet, especially in the former case - and just switching back to my normal text editor was enough to speed up my QWERTY again 30 seconds later!

I guess if you focus practice on finding that switch, for example with those games, that's just another skill you can learn like any other. Some people certainly have got very good at that with practice.