  The second functional derivative of the effective potential of pure fermionic
field theories is rewritten in a factorized form which facilitates the
evaluation of the renormalisation flow rate of the effective action in the
Wetterich equation. It is applied to the Local Potential Approximation in
cases, when the effective potential depends on scalar composites built from the
fermions. The procedure is demonstrated explicitly on the example of the
$N_f$-flavor Gross-Neveu model and the one-flavor chiral Nambu--Jona-Lasinio
model.
