A new power-law model of flame wrinkling for LES of premixed turbulent combustion has been proposed (Part 1, [1]). In the present paper, a dynamic formulation is developed to obtain the required power-law exponent from test-filtering the resolved scales during the simulation. First, it is shown that when the dynamic procedure is used to determine unknown multiplicative model coefficients that occur in classical models for premixed combustion, the approach is ill-posed asymptotically. Instead, it is well posed in formulations that aim to find unknown scaling exponents, this observation is used presently to formulate a new power-law dynamic model. The model is implemented in a LES combustion code in the context of Thickened Flame LES (TF-LES). Three-dimensional simulations of premixed flame in decaying isotropic turbulent flow are performed in several different parameters ranges. Comparisons between direct numerical simulation (DNS) and LES using different resolutions and thickness factors show that the proposed dynamic procedure allows the LES to reproduce the total reaction rate of the DNS quite well and irrespective of thickness factor and test-filter size. Comparisons between predicted overall turbulent flame speed S T as function of the r.m.s. velocity and experimental data show good agreement over a significant range of parameters. The simulations show that the exponent is not constant, but depends on time, turbulence level, and Reynolds number.