Is there a safe way to paint a little extra onto a subclassed control?

Question

Let's say you want to add a little extra graphical info to a Windows control. For example, you want to add drag/drop functionality to a listview (using the procedure discussed here), but with horizontal lines signaling the drop/insertion points as the user drags an item. (The control belongs to your own application.)

Is there a safe way to subclass the control and draw onto it directly? In my limited experimentation in trying to do this, I encountered some problems. First, it wasn't clear whether I should call BeginPaint and EndPaint during the WM_PAINT message, since the control itself would be calling those functions once the message was passed along to the default procedure. I also inevitably encountered flickering, since some areas were being painted twice.

I thought a safer way would be just to create a transparent overlay window and draw on that, since that would avoid conflicts with the default paint procedure, but I thought I'd ask before going down that road. Thanks for any advice.