A decent, good quality mushroom brush is an often over-looked piece of equipment in the armery of any serious mushroom forager. As mentioned before on the site, when preparing mushrooms it is important that you don't get the mushrooms too wet when cleaning them - all you need to do is to give them a quick brush to remove any dirt or bugs.
The best type of mushroom brush to use is one which has quite firm bristles, so as to quickly and easily remove pieces of dirt and gristle from the mushroom. Usually the underside of the mushroom picks up quite a lot of unwanted material so its a good idea to brush these gills, going in the direction that they grow, otherwise you end up breaking them as they are very fragile.
Some mushroom brushes are far too soft and it takes forever to actually get rid of the visible dirt, so its probably a good idea to just opt for one with reasonably hard bristles. Obviously if they are too hard then they will just tear chunks of flesh out of the mushroom, which isn't what you want. Some mushrooms are far more fragile then others, for instance it is quite hard to clean a hedgehog (Hydnum repandum) because it has very soft and delicate spines that appear beneath the cap of the mushroom. For a mushroom like this you may want a brush with far softer bristles, or it may just be easier to use a knife to remove any obvious pieces of dirt.
Some brushes may look quite cute and romantic, shaped in the typical mushroom shape with the bristles protuding below the (usually) wooden cap, but these aren't really that practical when it comes to it. They are a bit too big and so its hard to remove tucked away pieces of dirt, a pen shaped mushroom knife would be more suited. Another problem with these brushes is that usually they are too soft. They may be ideal for cleaning the types of supermarket mushrooms that exist, but for foraged mushrooms they probably wont be up for the job.
Some mushroom knifes exist that have their own brush tucked away cleverly inside the handle, and these are more then capable of doing the job. Its also quite useful because it allows you to clean the mushroom up when you're out collecting them in the wild, as it saves you making a mess back home and also allows you to brush out any insects back into their natural habitat, instead of bringing them home with you.
A mushroom brush should have quite hard bristles and not be too large, we highly recommend the ones which double up as mushroom knives so you can clean them up straight after picking them.