Official support for updated SRG->MCP mappings is already completed, but in the event that you require local mappings, this 'hack' can serve to inject your own custom mappings faster than the official schedule.
For Forge/FML, you will need to know basic directory management and git.
For LiteLoader, you will need to know the structure of Maven repositories, inspecting raw JSON files by hand, MCP's build tools, compiling LiteLoader from SVN sources, ANT, and some Google-fu.