One problem with using reusable metal filters, is that those of us who live in areas with hard water (Minnesota, I'm looking at you) sometimes find that the finest metal filters clog with hard water deposits.
One of my favorite immersion brewers is called the Sowden Softbrew, and every month or so, I'd soak the filter in vinegar to ensure it continued to allow coffee to flow quickly through the filter when it was time to remove the grounds.
But... it takes a LOT of vinegar to fill the brewer enough to get all of the filter submerged. To save vinegar, I put a glass into the filter, then poured vinegar down the spout until the level was high enough. Leave it overnight, scrub it clean in the morning, and we're good to go!