Just to expand on what andmiz said, a paintbrush is ideal for removing dust from instruments and front panels of radios etc. without damaging any buttons or knobs, or putting fingerprints on them.
Some materials - even some paper towels - can scratch screens and dials, whereas a paint brush will brush away dust and biscuit crumbs without damage.
Some of us, ahem, have a small paint brush in our flight bags for this purpose.
