Search for "The Japanese Abacus Explained" or "The Complete Abacus Manual" by Takashi Kojima. While these are vintage textbooks (1950s), the math hasn't changed.

Once you master the physical tool, these books teach "Anzan" or mental abacus. The goal is to visualize the beads in your mind, allowing you to calculate large numbers faster than someone using an electronic calculator. 3. The Soroban Manuals

You do not need to spend $500 on a course. You need discipline and the right worksheets.