The hand soap is extremely gentle so as not to strip the oils from the skin. The same goes for dishwashing liquid, which is good at removing grease and oil in hot water, but gentle enough on the skin.
Something like Formula 409, Fantastic or other general purpose spray cleaners designed to clean and degrease household surfaces have stronger solvents and surfactants, but you can try it in an inconspicuous place first just to make sure there are no problems. Startex is urethane, a waterproof polymer, so it should be immune to normal general purpose cleaners. Use a microfiber cloth. Follow it up with a separate microfiber cloth with clean water to remove any remaining cleaner.
Urethane is more resistant to alkaline cleaners than soft vinyl.
Let us know what works for you.
