This is a question with answer options. Goal: How can I clean the dust from knick knacks?

Which of the following methods is more reasonable for accomplishing this goal?

OPT: [-] Use warm soapy water and the flat side of an old toothbrush.; [-] Use warm soapy water and the bristle side of an old toothbrush.;...I think the answer is
Use warm soapy water and the bristle side of an old toothbrush.