Mapping results from different subjects to a unified model

I have 8 subjects and I performed voxels selection analysis. I want to visualize the selected voxels of each subject on a single brain. What I did is I considered the first subject brain as a reference model and for each subject, I multiplied the voxel index (since the voxels selection is based in the voxel space) by the affine transform of that subject and then I multiplied the result by the inverse of the affine matrix of the first subject. Not sure if this is the best approach, so I am wondering if you have a better suggestion?