On my ERC course they tought that a very minor wiggle of the front headlight is enough to get the other drivers attention.
If you have a fork mounted headlight (one that turns when you turn your handlebars) you can do it with a very subtle weave (bike stays almost straigh, but the hotspot of the headlight moves a few feet to each side). On a fairing mounted light (like the Ninja) where you need to turn the entire bike, it isn’t worth it since the weave has to be too exagerated.
Retro-reflective (aka safety) vests are a good investment.
Modulating brake lights do exactly what you are doing – they flash thebrake lights whenever the brake light is on. A quick tap of the brakes before you apply them in ernest (just to wake up a driver behind you) and a quick flash of them when stopped as someone comes towards you are good enough imo (especialy given the inconsistent legality of it).
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“The two seconds between ‘Oh S**!’ and the crash isn’t a lot of practice time.”