How do I clean the buckle on the Graco 4Ever DLX?

To clean the buckle, recline the seat, locate the metal retainer, rotate it up through the shell and pad, and pull out the buckle strap from the front. Soak the buckle in a cup of warm water and gently agitate it while pressing the red button several times. Do not submerge the buckle strap or use soaps, household detergents, or lubricants. (Page 7)