Ion channel simulations require the presence of large bath regions for accurate treatment of screening. There being of such bath regions make the mesh domain of Poisson equation large and leads to either a large number of grid points with fine mesh resolution or a small number of grid points with very coarse discretization. From bulk simulations a coarse mesh is sufficient for describing the baths using the P M scheme. However, a fine resolution is required in the channel domain because of the highly charged nature of these regions and the presence of spatially varying dielectric regions. Besides the ultimate interest is to study the channel behavior in terms of ion permeability, selectivity, gating, density, etc.... In other words, it is better off to put more computational resources in the channel region, and bare minimum in the baths to reduce the overall computational cost and speed up of simulations from weeks to perhaps days instead. A scheme based on the grid focusing method has been developed that makes it possible to satisfy the requirement of large bath region and a fine grid resolution in channel at the same time in a computationally effective way. This methodology is capable to have multiple fine mesh domains, which may be needed to describe multiple pore channels like OmpF porin, or an array of ion channels sharing the same bath regions or even having yet finer meshes inside a fine mesh for relatively large channels with narrow ion passages like Nicotine receptor channel.