I'm developing a content type for Plone 4, and I'd like to block all user, group, and context portlets it may inherit from its parent object. I'm thoroughly confused by the documentation at this point–in portlets.xml, <blacklist/> only seems to address path-specific blocking. <assignment/> seems like what I want, but it seems too specific–I don't want to manage the assignment for all possible portlets on my content type.
There are hints that I've found that customizing an ILeftColumn and IRightColumn portlet manager specific to the content type, but I can't find any good examples. Does anyone have any hints or suggestions? I feel like I'm missing something dead simple.
Do the assignment to your portaltype live on a site via Sitesetup (controlpanel) -> Types -> "Manage portlets assigned to this content type". 
Then export the configuration via ZMI -> portal_setup -> Export-Tab -> select 'Portlets' -> click 'export' on bottom. 
Extract the types/YourType.xml-file and copy the relevant parts in your package's profiles/default/types/YourType.xml.
Plone Content Type-Specific Portlet Assignment