It does take s little practice but not too much. The awkward positions are easy enough after a few weeks.
I chose binary for two reasons. First, it is occasionally useful to count that high on one hand. Second, the education when he’s older. I hope this will give him a note intuitive understanding of different bases. And binary is specifically useful for understanding comported and software development. I dont intend to push him toward a career in software but I think there’s a fair chance he chooses that anyways.