DrDamn Helps steady the hands, obvs.
The soldering is actually very easy - there’s two points where you need to solder a small wire onto an existing contact. They’re easy to get to and well isolated from other stuff. It’s also optional - soldering is only required if you want to be able to remap L3/R3 and the touchpad. If you don’t care about those, you can skip the soldering bits entirely, it’s just taking the thing apart and switching around some ribbon cables otherwise.
Mapping buttons is easy. You hold down the wee button in the middle of the attachment until a red light flashes. Then, you hold down the button you want to map and the paddle you want to map it to at the same time until the light flashes again. That’s it. Tried it out briefly with FFXIV last night and it seems to work very well.