easiest way to deep clean washing machine?

Front loader or top loader? Front loader: pull the door seal back and wipe out the fold, that's where the black gunk and the smell live. Pull the detergent drawer right out and soak it. Then find the drain pump filter, usually behind a little flap at the bottom front, and put a towel and a shallow tray down first because a lot of water comes out. Coins, hair and lint all end up there. Finish with an empty hot cycle with a washer cleaner or a cup of bleach. Top loader: fill it on the hottest setting, add the cleaner, let it sit an hour, then finish the cycle and wipe under the rim. Either way, bleach or vinegar, never both together.