In those branches of physics involving quantum many body systems, mean field states are a good starting point for any theoretical study. One of the advantages of mean field states is the existence of generalized Wick theorems that simplify the evaluation of operator overlaps. Unfortunately, the number of terms to be considered increase with the double factorial of the number of creation and annihilation operators in the overlap. This and other problems that appear when the mean field states are of the Hartree Fock Bogoliubov (HFB) type can be easily handled introducing fermion coherent state techniques and the pfaffian. In my talk I will discuss this technique and the applications involving HFB states in the context of symmetry restoration and configuration techniqes common in low energy nuclear structure calculations.