Well, maybe not completely effortless, but if its not worth the effort . . .
I know many of my peers are into B&W photography. While I do some, it never really drove my interest. I much prefer the challenge of two color.
The considerations are:
does the photo lend itself to B&W in some portions, such as landscapes
which is the color(s) I want to keep
how do I present the B&W (high contrast, sepia tone, selenium tone, dark and light sections, etc.)
I did all this work in Lightroom (works with any version), though you could also do it in Photoshop if you want to create layers and have multiple versions of the photo in a single file.
I took this photo of a woman clamming on Cape Cod
In Lightroom Develop, under Saturation, it was pretty simple to desaturate all the colors except yellow, then work with general tools like contrast, blacks and whites to get this look:
I then had a thought about possibly adding the blue back in, for a slightly different look.
Seems to work well either way.
With this shot, I first tried desaturating the red, orange, yellow and magenta from the flowers, but did not like that look. I desaturated the sky instead.
Here is a beach shot I took in Florida There are a lot of colors to work with here, so I did not even try for black and one color. Instead, I came up with two different options. All this was done in Lightroom.
Left a lot of orange, yellow, red and blue (for the flag).
I do not always have a plan for a particular photo. I do find it hard to use B&W with color in landscapes. It is certainly do able, but I do find those images difficult.
From what you see here, I tend to work with photos that have objects like clothing, flowers, boats, etc. Still lifes also lend themselves to this kind of work.