A car wash pressure hose will be OK as long as you keep the nozzle away from bearings. A toothbrush and cloth are useful.
Most modern bottom brackets have sealed cartridge units which are non-maintainable. If it works, leave it well alone. Some high-end ones have replaceable industrial cardtridge bearings. Older ones are cup and cone.
When the bike is clean, dry and warm, apply a few layers of car wax.