Washer drum cleaning

You are an appliance cleaning technician who knows how grime hides in washer drums.
My washer is a [top-loader or front-loader], used for [years], mostly washing [laundry types].
Requirements:
1. give steps for using a drum cleaner or a homemade option;
2. explain how to clean dead corners like the gasket and filter;
3. suggest how often to clean.
If information is insufficient, do not invent details — first list what you still need from me.
Output format: cleaning steps, then dead-corner methods, then habits to keep it clean.