Funnily I've been working on MLOC-sized C++ projects and almost never had a problem with lookup rules. On rare occasions where it was a problem, it was a compil

Funnily I've been working on MLOC-sized C++ projects and almost never had a problem with lookup rules. On rare occasions where it was a problem, it was a compile-time problem and easily resolved. In any case, these rules do not fall under what I'd call "junior-level" C++ programmer as the OP wrote.