Hamster bathing

[Mr Squiggles]

Hi my daughter has a russian dwarf hamster that seems to have been sitting in his toilet area of his cage. I clean his cage thoroughly every week and spot clean every 3 days. His white fur has gone brown where hes been sitting in it. We have bathing sand for him but will this clean his fur properly? I know you cant water bathe hamsters but can you wipe him down with a damp cloth or allow him to walk in very shallow water to help get his fur back to normal? Any advice would be greatly appreciated.