It doesn't take long, though the number of nodes it has to look at will affect the time taken, there'd have to be a lot for it to take more than a few seconds.
What do you see in the Python console window when running from the File menu ?

To make an MC6, goto the Material room and click on the "+" button at the bottom of the Library palette. You'll be asked to select either a "Single Material" or a "Material Collection", choose a collection.
To attach an MC6 to a post you'll have to change the extension to ".txt" (alternatively tell me what figure and texture set your using, as I may have them).