When emulsion painting a ceiling with paint of the same colour as is already
on, I have great difficulty detecting the wet-edge of where I have just
painted. And this makes it difficult to know where to apply the paint next.

Is there anything I can do to make the just-painted wet edge show up better,
so I do not end up with missed patches?

I was thinking that a difference between wet paint and dry paint is that
light is reflected better from wet paint. So I wondered if it would help to
get a bright, cold-running light, such as a 500W security light, and point
it at the ceiling from the floor. Has anyone tried this, and did it help?

Anode.