Rundll32.exe doesn't do much of anything. It simply executes an application program interface (API) in a DLL file, which is what makes this little program so ubiquitous and, as you noted, powerful. Using it for various purposes really requires that you learn the APIs available in different DLLs, which ones will support Rundll32 and how to use them. Instead, I recommend that you use the tips for using Rundll32 that you find on the Internet.
This was first published in August 2003