You could go even easier and just switch off your main at the panel altogether. You could then run an HD extension cord from your generator to an outlet, you'd have to replace the female end on the cord with another male end to get it to plug into both the generator output and any wall receptacle. At only 900w, you wouldn't need to worry about overloading any of the household circuit, as the outlets themselves should easily handle 1300w. Then just switch out the circuits you don't need on the circuit breaker panel until you are left with just the essentials for lighting. It is a simple fix that doesn't require rewiring your lighting fixture circuits.

Of course, you might have to guess at when the utiltiy power comes back on, but if you live in a neighborhood you will know soon enough.