how can i set up dusk to dawn outdoor lighting ?
Any way you like. 


Connect your in-wall timer to a relay with a 1-pole coil that
controls two poles.
Replace your timer with a two-pole timer.


To me, either of those are "simpler" than anything having to be done to three separate locations...but none of it is very complex.


Add photosensors.
Replace the lights with fixtures that have built-in sensors (if they are not currently LED light fixtures, that's one
more reason to consider this approach.)
depending why you have them and what purpose they are serving, use motion sensors instead of photosensors so the lights are only on when needed. Lower electric bill and less light pollution.