We'd suggest keeping our bikes clean with water only, or a very mild soap and water solution. Clean with a sponge or soft cloth rag. We do not spray directly with a pressure hose, as water under pressure can potentially penetrate into bearings. For cleaning a matte finish, we recommend products such as Windex or Simple Green. To keep your matte finish with a true matte look to it you would want to avoid excessive scrubbing this will actually buff and shine the matte finish to a shiny finish.
Note: After cleaning your bike, you need to re-lube your chain. Keeping your chain clean and lubricated will result in better shifting performance and longer life of your drive train.