How do you use ReShade 2.0?

Maybe I'm being stupid, but it's not intuitive at all on how to use ReShade without manually fiddling with every shader.

I did used to use SweetFX and it was as simple as adding a game and importing a preset with all preconfigured values.

How do you do that with ReShade? The UI is terrible (sorry, but it is), and there seems to be little to no documentation bar the 5 steps on the home page.

You aren't. It is not intuitive. That's why it's being restructured completly: See the 3.0 section of this forum (overview: reshade.me/forum/general-discussion-2/2014-reshade-3-0-progress ).