"Stuart Noble" wrote in message
...

I've struggled with this problem, especially white on white. I reckon a
headlight might work but haven't got round to trying it

An interesting idea, though I suppose a battery light around the head would
not show up well in ordinary daylight. I've seen plasterers use a strip
fluorescent light in a vertical position, standing on the floor, in front of
a wall they were working on. If such a light is helpful for work on a wall,
it suggests it may be helpful on a ceiling if positioned suitably. Though
the plasterers would be looking for undulations I suppose, whilst I am
looking for wet edges, which is a bit different.