How can I retrieve the ModelAdmin given the model class or an instance?

[Marco Rogers]

I'm retrieving a model using django.db.models.get_model. The view is
receiving a post from a form generated by the ModelAdmin. How can I
get a hold of that ModelAdmin instance so can then get a hold of the
ModelForm? This will allow me to process the post (validation,
related objects, etc). The ModelAdmin has a reference to it's model,
but the reverse doesn't seem to be true.

The way I'm doing this right now is bad juju. The AdminSite keeps a
registry of models and ModelAdmins so I'm doing this:

modeladmin = admin.site._registry[model];

Obviously using this internal registry is a bad idea. I was looking
for a more official api similar to get_model or one of the following:

modeladmin = admin.site.get_admin(model)

Even if this just returns the instance from the registry like above.
Or make it accessible through the model like one of the following:

modeladmin = model.get_admin()
modeladmin = model._admin

Any help with this is appreciated

Now a litlte more context. Like I mentioned above, what I actually
need is a ModelForm similar to the one generated by the admin site. I
have a custom admin view that receives the post from an add/change
form. So to process that post I need the equivalent ModelForm.

If there is an easier or more idiomatic way to write custom admin
views, I'd appreciate if someone pointed me in the right direction.