I wonder if this topic might be vaguely related to your question:
https://ukcaving.com/board/index.php?topic=25851.0
(I'm thinking - wider angle lens, get nearer, better illumination, so more reliable auto-focus?)
Also, if you're "painting" with light, I'd have thought that keeping the lamp in a fixed
position (on a tripod maybe?) whilst constantly altering the angle it's shining at, might help?
Other than that - brighter lamps / more of them? (There are some very cheap, incredibly bright lamps intended for bicycle use available these days, on Amazon, etc.)
One other thought; if you use a makeshift Fresnel lens (which could be as simple as a thin white plastic bag) over the lamp, to spread the light, you might not need to move the lamps at all.)
But don't take any of my suggestions too seriously as I'd be the first to admit that I'm a rubbish photographer.