I always cringe when people are discussing washing instructions and tell people to twist their clothes in a towel. To me this gives lots of wrinkles. After I sink wash, rinse and squeeze out as much water as I can without twisting, I lay out the shirt on the towel, smooth the wrinkles out and then roll up from the bottom of the towel. I do fold it in half and yes, I stand on it but I don't twist. Then I shake the garment out before I hang it.
I also carry a small, travel size empty bottle with a sprayer top on it. If something does wrinkle I will spray it with water and shake it to get the wrinkles out. I have 2 Lands End shirts that are supposedly the identical percentages of fabric content (cotton/modal) and one does come out slightly wrinkled while the other one does not. I do have to spray the wrinkled one and it will not be making the travel team this year!
I agree with others to do some practice sink washes and work on your technique, lol.
I also sink wash in a 2.5 gal ziplock back so I have more room than a typical sink can provide. If you are traveling with someone else it also allows the sink to be accessed while the washing is being done.