Visibility is the intersection of psychology and optics.
Optical visibility is rarely a problem, especially if you have a reasonable amount of lights/reflectors. I agree that the edge cases tend to be low sun, shit weather and being lost in clusters of city lights, but most of the time this isn't a problem because you aren't in conflict with whoever can't see you. (ETA: I should probably add A-pillars and inappropriately designed large vehicles here. Those can render you invisible in any conditions.)
Psychology is about attention. Catching a driver's eye for long enough that they accurately assess your position and velocity. This is mostly a function of putting yourself where they're going to be looking for cars (because what they're looking for is cars), and being somehow interesting (weird bike, unusual cargo, being a target for sexual harassment, whatever). Space-lemon tactics do very little to help, and might actively hinder.
And of course nothing will make you visible when they're not looking.
As ever, the best approach is to assume they haven't seen you, and that if they do, they're probably going to try to bully you anyway.