How does this method work?
For a skill to generate revenue, it must translate into a result that the customer understands. Instead of 'I know Excel', 'I organize the weekly sales report in a single file' is a clearer offer. Match your skill level with your delivery promise; Don't take on responsibilities you don't know about in areas that require expertise, such as critical accounting or security work. Your portfolio is the output you can show, rather than just saying what you know.
Evaluation with a concrete example
For an example, you can edit the sales table of an imaginary store. Show the messy data first, then the clean table and three questions the manager can answer. Do not publish real customer's data without permission. Explaining why the work is useful is more understandable than listing all the formulas used. The customer buys the time savings or error reduction, not the technical tool.
Your first application: what should you have?
Tie your skill to a single customer problem, prepare two sample jobs, and write out the scope of delivery. Save the most time-consuming step after each job; Create a checklist for repetitive steps. Strengthen customer bottom line and delivery reliability, rather than simply learning more tools to raise prices in the future.