Kinetic simulation of plasmas with detailed excitation and ionization collisions presents a significant computational challenge due to the multiscale feature of the collisional rates. Direct numerical simulation of these collisions using Monte Carlo method requires a large number of samples to resolve all the fast collisional time scales, which is often not necessary and make the simulation very inefficient. In this paper, we present a coarse-graining method to reduce the complexity of detailed excitation and ionization kinetics. The method is then applied to the standard Monte Carlo collision algorithm for simulating a partially ionized Hydrogen plasma. We show that the computational cost can be reduced at minimal loss of accuracy.