Zaid Alsalami, Shaykh Dr Zaid Alsalami is an Iraqi born scholar, raised in Australia. He obtained a BA from Al-Mustafa University, Qom, and an MA from the Islamic College in London. He also obtained a PhD from... Answered 3 months ago

Bismihi ta'ala

Touching something will not break one's wudhu`, unless it is the touching of a dead human body after it gets cold, and before it is washed. 

For anything else, najis or not, just touching it will not break wudhu`. Of course, if it is wet, and your hand gets contaminated with najasah, all you need to do is wash it. 

As for touching something dirty, the same thing, and no, from a shar'i perspective it is not necessary to 'wash' your hands if it is just dirty and not najis. 

And Allah knows best.