tissues

Alsalamo Alaykum, i have a very small question: After a man urinates, must he use water to cleanse his penis? Sometimes i'm at a public bathroom, and i can just use a tissue to wipe myself after the urine without using any water..i dry my penis from urine, but using no water. is that permissible? also, sometimes at work i feel like i wanna urinate, but i hold it so that i don't have to make wudu' again since sometimes it's cold and i have nothing to dry myself with, and i don't like to walk around feeling wet. Can i pray then urinate? or am i not allowed to pray while i need to urinate? i heard that i'm not allowed to pray while i need to urinate since i won't be able to focus. but what if i can focus?