instant meditation - Imagining things and people in their decayed/old form?

When I see something or someone beautiful, would it be good to imagine that thing or that person in decayed/old form? This idea came to me when I was reading about "Dasa sanya" (i.e. *dasasaññā* or "ten perceptions"). Will it be bad practice to take "Vipassana meditation" in a mental image form, like focusing on the decayed/old form of the particular object or person, instead of focusing on what I see?