I use a lightweight workflow using two small tools that are ~1 MB combined, and uses <10 MB of RAM combined. This setup gives you instant control via your mouse scroll and keyboard, without much clicking.
Install ClickMonitorDDC and f.lux.
1. Hardware Control: ClickMonitorDDC -
controls the actual monitor backlight via DDC/CI.

In the image, blue icon displays volume which is at 60, pink one displays hardware brightness which is at 0. Both can be controlled via mouse scroll.
- The Shortcut: Drag the icons to your system tray (next to the clock). You can then simply hover over the brightness or volume icon and use your mouse scroll wheel to change levels.
- Why it's better: No need to touch your monitor’s physical buttons and no clicking anything. Just scroll from any window.
2. Software Dimming: f.lux
When your monitor is already at 0% and you still need it darker, use f.lux.
- The Shortcut: Press Alt + PgDown to dim the screen beyond the hardware minimum.
- How it works: While this doesn't lower the actual backlight power, it adjusts the colors to simulate a dimmer screen, effectively reducing eye strain.
This combo is the fastest way I've found to manage light levels without adding any bloat to your system.