KiCad-nightly V6.99 has an option to load an image into the PCB editor with PCB Editor / Place / Add Image. This image can be flipped and scaled.
You can use this as a template during reverse engineering. For more, see:
Do note however, that projects saved in a nightly version, can no longer be opened in the stable KiCad version.
It would have been nice if you could create a netlist from this in the PCB editor, and then show ratsnest lines in the schematic, but this is not supported. What you can do is open both the schematic and the PCB editors, make connections in the schematic, F8 them to the PCB and combine that with real tracks drawn over the image.
Another valuable resource are the datasheets and application notes of used IC’s. Quite often the real circuit is similar to those application notes and this can help with re-creating the schematic quicker.