I have published two articles with the results of my qualitative data but now I am writing an article that report both quan and qual results. How do I report the quan results again without self-plagerising and re-reporting a substantial part of my work again?
If you are writing a mixed methods article, then the idea would be that you are integrating the results from your different methods, rather than simply reporting the separate findings – which means you will be writing about them quite differently from when you reported just one set. You should be able to take your conclusions much further with the additional data and results than you could in your previous articles. You will also be able to note that some results are previously published, and cross refer to those articles.
I agree that you will write differently when it is a multi-method study. Still, you have to provide a reference to your previous work. Since the results are the same, only the quantitative part of your multi-method publication is the real/only innovation. Why not writing a quantitative study instead of a multi-methods study?