I’m reposting Mike Whitby’s post:

On occasion you may have a module which requires both EAV and flat resource setup classes, in this situation you can instantiate a setup class as this note shows.

Eav:

$installer = Mage::getModel('eav/entity_setup','eav_setup');

Flat:

$installer = Mage::getResourceModel('core/setup','core_setup');

You can then continue with the setup script as you normally would.

Thank You Mike!