There is just about nothing that can affect pure gold. Just scrubbing on it can make scratches, as its very soft. Best is a ultrasonic cleaner for that, also for silver.
Silver cleaning can be done with several methods. Acidic is one way, but also caustic works. Washing Soda, baking Soda, there are a number of tips on YouTube for that. And it works pretty quick - inside a minute.
It depends very much of course on what the "dirt" actually is. Is it real dirt - which can be anything - or the typical black silver corrosion, that is caused by a reaction with sulfur.