Somebody has already said this, I think, but voice typing is good if it would work for you. If you use Google Chrome on a PC, then you can set up voice typing on Google Docs which is really useful.
I've never managed to get Microsoft speech dictation working but that may just be me.
Depending on your budget, apple have some great products with dictation built in and Cortana is worth using on Windows to do internet searching - I m currently experimenting with Google Voice commands.
If your voice is good enough for dictation however, dragon Dictation on a PC is brilliant but you do have to have a powerful enough machine and it is expensive if you want all the features.
I find swipe keyboards the best, the new Windows 10 build (whatever that actually means) has a one-handed swipe keyboard, it's easy enough to put a Swype keyboard on an iPad and the Google keyboard on Android works really well too. You just move your finger around on the keys and you don't have to lift it up and down which makes it much easier for me. You may well already use this but it's worth looking at YouTube demonstrations to see what I'm talking about if not.
I find a Rollerball Mouse really useful especially the larger ones. They are expensive but I found mine on eBay for a lot less money.
I know people who like keyboards with key guards and large keys but I personally prefer small keyboards with low profile keys so that I have to move my hands as little as possible
Putting any sort of feedback such as keyboard clicks helps me and there are some good programs and packages for accessibility but they are quite pricey.
I love swype keyboard but touch screen devices are my nemesis. I can refile and move everything without even knowing so I quite like connecting my touch screen devices to my PC and using them as a swype keyboard but I'm not sure about the security of doing this.
Some phones have a setting that ignores repeated taps but I do think there's a lot more that could be done in relation to accessibility and dexterity issues both in terms of device manufacturers and website design (if only I was clever enough to do something about it
Sorry for the ramble - you may well already have
tried most of these things and if you have any other ideas, I'd love to know because we're going to be more dependent on IT for everything in the near future and my out of control hands do worry me so I like to try anything that might help.
Hope you find something that works for you.