Something like this. I shoot LF and my maximum aperture is never greater than 5.6. When I'm indoors, out at dusk, or I'm shooting at night, I have to carry a very high-power bike lamp with me. There's no other way to get fine focus.
Most digital cameras should have a shading feature on the liveview, which should highlight what is in focus and what is not. I forget the proper name for this, because I've never used it.
Lastly, you can always but a split-image focusing screen, which is I assume what you mean by a "sliding moon". They're pretty easy to install, and usually run somewhere between 50 and 100 USD. I have one in my D7100, because most of my lenses are manual.