Was the use of propaganda the main reason why support for the nazi party grew in the years 1929-32?

No.

The line between political campaigning and Propaganda may be a blurred one, so opinions on this may vary. When the Nazis were in power there was a ministry of propaganda and the use of black propaganda was widely used against the Jews. But the Nazis made great advances in political campaigning, making use of the radio and aeroplanes to reach a greater proportion of the population than ever before.