How to Make Lots of Mistakes Typing

People who type in only one language, or who use only the occasional foreign word here and there, have no concept of the brain malfunctions that occur once one tries to use multiple keyboards (physical and virtual). For example, during a spring break trip to Munich a few years ago I learned that German keyboards put the Y and Z in opposite positions than American keyboards do, so my emails developed a tendency to have half the Ys typed correctly and half replaced with Z. Czech keyboards also do this Y and Z reversal, as well as having to produce a lot of accented letters. You can get any Windows computer keyboard to toggle between different virtual keyboards so that for English typing it is set for the English keyboard, and so on. (I must say I find the French keyboard really alarming as less of it is familiar than the Czech, which was a great surprise.)
It did not take me all that long to get reasonably familiar with the basics of using the Czech keyboard, since most of what’s different is on the number keys, and I rarely type numbers if I can avoid them anyway. It is true I sometimes confuse the ě and š keys, and č seems to bother me, while ž is in a surprisingly hard to type spot, but my main complaint is that there is no apostrophe that I am aware of. Thus, I have it fairly well ingrained in me that Y and Z are reversed when I type Czech, and that if I want a Z I had better type the key that is labeled Y. The difficulty is that I often type small amounts of Czech or English using the wrong keyboards because it seems simpler than toggling to the other keyboard for a word or two. This means that I will never, ever, really train my brain that one keyboard is solely English and the other is solely Czech. Thus, every time I transcribe an article in Czech, my typing is not only considerably slower than if I were typing English, but I have mental contortions about Y and Z and have to proofread the results to see if there are any unlikely-looking words. And, of course, sometimes the unlikely-looking words are entirely correct and I just don’t know what on earth they are.
This, mind you, isn’t even getting into my use of the Nota Bene Czech keyboard, which I often use when typing in that word processor. Nota Bene doesn’t use the Windows Czech keyboard, because it has its own, which is not completely the same—it doesn’t make ú but only ů (although you can get ú, and much weirder letters from languages I can’t identify, using F6), and it doesn’t use the Caps-Lock key to make letters such as Š and Č, but relies on the F6 menu for those. Since I often type the name Štyrský, it has become one of my most-misspelled words in any system. Let's not even think about its declined forms and their endings.
And yes, back to the Windows keyboards, they don’t work perfectly with all programs. I can set Windows to Czech to use with my Lingea Lexicon Czech-English dictionary, but if I type the ř key it displays as ø (suggesting a strange mix of Czech and Norwegian). Fortunately the dictionary recognizes that I mean ř rather than ø, but I don’t know how it does that. Endnote 7 did something similar, but printed out all my bibliographies with the wrong letters (why I don’t use Endnote anymore).
Thus, it is not purely a matter of repetitive stress injuries that I no longer type over 100 words per minute, and make peculiar mistakes on a routine basis.