I have the same problem.
At first sight DrawVisualizationHUD() seems like the correct way of doing it.
But it does not work at all. No matter what you draw on the supplied Canvas, it never shows on screen. Flushing the canvas does not help.
Searching the internet returns zero examples of using DrawVisualizationHUD() to do anything at all. Searching Unreal Engine repository also does not help - the DrawVisualizationHUD() method is there, but never used in any visualisers.