Kujau was not the first person to forge paintings by Hitler.
After Hitler became a world-wide sensation in the early 1930s, his former associate from his Vienna days before the First World War, Reinhold Hanisch, produced some paintings which he claimed Hitler had given him at the time of their association, but which were almost certainly forged by Hanisch himself.
The business association between Hitler and Hanisch had involved Hitler copying Vienna street-scene from postcards and Hanisch selling them to petty art-dealers. The association ended when Hitler brought a court action against Hanisch for defrauding him of the sales proceeds.
https://en.wikipedia.org/wiki/Reinhold_Hanisch
On 20 July 1923 Hanisch was sentenced by the district court in Vienna to three months' imprisonment for theft. Hanisch was divorced on 17 April 1928. After 1930, Hanisch worked as a painter. He produced watercolors, which he sold as alleged works of Hitler from their years in Vienna. Hanisch often painted pictures of flowers in the style of the painter Olga Wisinger-Florian, which he sold as Hitler originals. To cover up the fraud, he had his friend Karl Leidenroth authenticate the forgeries. Nevertheless, on 7 May 1932 Hanisch was sentenced to three days in jail.
With Hitler's appointment as Chancellor in the spring of 1933, Hanisch became an object of interest. The Bavarian journalist and anti-Nazi Konrad Heiden, who was writing the first authoritative biography of Hitler, turned to Hanisch, then the only known witness of Hitler's Vienna period. Hanisch readily supplied information and was paid well. In the following years Hanisch made money from numerous interviews with national and international newspapers. Hanisch’s memoir of Hitler posthumously appeared in 1939 in The New Republic.
Although Franz Feiler, the son of Hanisch’s former landlord, was friendly with Hanisch, Feiler had acted since 1933 as a Viennese emissary of Hitler, on whose behalf he bought genuine and fake Hitler pictures in Vienna, and brought them to Germany. There they were either destroyed or transferred to the archives of the Nazi Party in Munich. In Easter 1933 in Berchtesgaden, Feiler gave Hitler some of Hanisch’s “Hitler pictures”. These Hitler recognized as forgeries, and instructed Feiler to file a complaint for fraud against Hanisch. Feiler followed Hitler’s instructions and on 6 July 1933 accused Hanisch of fraud. After spending several months in prison Hanisch continued to forge Hitler pictures.[3]
On 16 November 1936 Hanisch was arrested. During a search of his rented room the police found, in addition to manuscripts about Hitler, more Hitler fakes. On 2 December 1936 the Vienna regional court sentenced Hanisch to prison for fraud. Hanisch probably died February 1937 in detention. Hanisch fakes occupied Hitler’s staff for years after Hanisch’s death. On 21 October 1942 Hitler ordered Heinrich Himmler to destroy three fake Hitler pictures, as well as other documents.
It is likely that some of the forgeries by Hanisch are still in circulation as Hitler originals.