That's quite interesting, as I've had an opposite experience (substitutions ahead). Switching to dvorak lifted my speed on it as well as qwerty, and my Japanese

That's quite interesting, as I've had an opposite experience (substitutions ahead). Switching to dvorak lifted my speed on it as well as qwerty, and my Japanese has only helped my French. There was certainly a lot of weirdness at the moment the two sides reached the same level– if I froze up for a second, I might start mixing in French words or reaching for Command-Q with my left pinky. The only real obstacle has been slowdowns from going 6+ months without using one or the other which isn't all that hard to work around. For typing, triggers are anything with a 'd' in qwerty including the word 'dvorak' ironically, 'the' in dvorak. With language, the rhythm and intonation are usually a dead giveaway. In your case however, the subjects are quite similar. Colemak is a change from qwerty, but it's not as overtly different from qwerty. That might make the transition easier, but it could be one of the reasons switching between them is hard. Spanish and Japanese is also an interesting combination as the sounds are, at times, quite similar (and not just due to the Portuguese loanwords, a la パン or カステラ). Perhaps your difficulty is in finding distinctive enough triggers.