There a number of techniques which are incorporated into this aspect of Art. There are also various apps and workshops that can be used to create the photomontage including Paint, Photoshop and other Digital imaging websites.
The Dada movement claimed to be anti-art; it had a strong negative & destructive element. Rejecting all tradition, they sought complete freedom. Dada quickly spread from Zurich to other European cities. Dada artists claimed to have invented photomontage.