If you want to use external outboard effects and/or mix in an analog fashion and the 2 internal Audio Ouputs of the Push 3 are not enough, you can get the OctaWave – a pocket-sized high-quality ADAT to Analog Converter.
It gives you 8 separate mono channels (which are also control voltage ready, so it can be used to control your analog synthesizers) on 3.5mm Jacks.