- Learn a different key layout like Dvorak (investigating)
- Switch between two different keyboard every hour or so (didn't try yet)
- Think before you type in order to minimize mistakes and hence total amount of writing (new idea)
I would advise against switching between keyboards often. Not only do you have to mentally switch, you likely have to readjust to the new typing experience too, and that's a needless burden, in my opinion. I did this while getting used to the ErgoDox, and it was a painful, inconvenient experience.
Thinking before typing does help, not only by reducing mistakes, but by having a better flow of typing, and that helps a little too, I found. If I feel less stressed about mistakes, or about my speed, then I will type better, I won't try to rush and make shortcuts, but type properly, and my hands and fingers like that.
As for the layout: Dvorak is orders of magnitudes better than QWERTY, but it is very different. You have a lot more hand alteration, and a lot less rolling (typing a few keys with adjacent fingers, kind of rolling sideways on the keyboard). If you happen to prefer alteration (I do), Dvorak is for you. If you don't, try something like Workman, Colemak or Norman. With that said, Dvorak has its issues too: the L key is in a terrible position, for example. That's one of the reasons I'm about to switch to my own layout, inspired by Dvorak, and keeping many of its properties, but getting rid of some of the issues I experience with it.
So what else is there to investigate? Any particular technique for pressing buttons or moving hands?
Tenting was suggested already, but if you're using an ErgoDox, I would also suggest moving your modifiers, or at least Shift, to your thumb cluster, and turning it into a one-shot modifier. That is, you tap it, release it, and the next key within a few seconds will still be shifted. This means you don't have to hold the key, and thus, reduce the work your finger has to perform, and you move it to the thumb cluster, so its under a strong finger, and you don't hurt your pinkey.
I've been using this setup for a good while now, and it has done wonders to my feeling of comfort. It does take some time to get used to not hold keys, but once you're there, the difference is huge.