Being lazy and busy means more straightforward editing methods to be used. I used to do the basic editing with curves and add the vignette by hard way. Now I have improved the process with much more simple steps on GIMP:
- Duplicate layer.
- Set layer mode 'Soft light' and opacity 50% for duplicate.
- Select 'Blend tool', set 'Gradient' for reverse, and choose 'Radial' shape.
- Use blend tool to draw line from middle of the picture to one of the corners.
And that is all you need to do, except maybe a little sharpening. Especially this way the vignetting can be made fast and easily. You can also use layer painted black to do the vignetting, but duplicate layer set for 'Soft light' and 50% opacity also increase the overall contrast for the picture, which usually just improves the picture.