Daniel Jacobson defines the multilevel approach like this:

Multilevel theories distinguish between an intuitive and a critical level of moral thinking. The intuitive level comprises commonplace rules and emotional dispositions, justified by the utility of their acceptance; whereas the critical level determines true moral judgment and genuine obligation. Such a theory separates its criterion of right action- such as the maximization of net happiness- from its recommendations for moral thinking. This separation enables the theory to hold that good people will often be disposed not to perform, or even to aim at, right action.

Note that Louis Pojman also gives a multilevel defence in Ethics: Discovering Right and Wrong,  page 112

For full text of Daniel Jacobson's chapter on act and rule utilitarianism go to:

http://quod.lib.umich.edu/cgi/t/text/text-idx?c=phimp;rgn=main;idno=3521354.0003.002