When doing ghusl or wudu how do I ensure if a part is completely washed if that part was already wet?

Whenever I do ghusl or wudu My feet and my hands and private parts get wet(as sunnah). Then when i start purifying(wudu or ghusl) myself I can find *itminan*(certainty) that I have washed the part completely. 1. My First Solution was to drying parts and and dipping parts that I can't was in a water container(like feet because floor is wet). But it takes significant amount of time (10-15 minutes). 2. My Second solution was to rub every such part with soap, the soap also gave an indicator how much i've washed.But its also time consuming. **I just wanted to ask how do you deal with this problem? And how do i do this when I am in a public bathroom without soap and towel?** Kindly Share What Allah Has Given You!