these boycotts are mainly about avoiding buying from these companies, not working at them.
if you do wanna help though, you can try to waste as much of their money as possible, for example by slacking off or giving customers extra food (of course if this is your only means of living not getting fired should come first)
it’s basically just a shared random number generator on a timer (it’s slightly smarter than that but that’s the gist), so as long as you know the start time, the current time and the starting point for the RNG, both parties can get the same result without having to ever communicate