3-4 drops of antibacterial dishwashing liquid or a little bit of Chlorhexidine in a bowl or pan of warm water. Use a toothbrush to scrub off the offending poo and rinse the area and let dry, or use a blow dryer to speed it up.

Usually, if all I need to do is disinfect it, all I will do is spray it down with Isopropyl Alcohol and use a blow dryer to evaporate the alcohol quicker...

Hope this helps