PiShrink is a bash script that automatically shrink a pi image that will then resize to the max size of the SD card on boot. This will make putting the image back onto the SD card faster and the shrunk images will compress better.
This tutorial will teach you how to add a button you ca use for powering on and off your raspberry pi. This uses the gpio and you may require to solder wires to your button. This is best done with a momentary push switch.