That dang ivy and oak is a pain for sure.If you come across a plant called (Touch me not/jewel weed) Grows in the same places as oak/ivy has an orange flower and the seed pods explode with a touch.
If you make a salve out of the aerial growth and a carrier like coconut oil.It will pull all the bite out,stops the oozing and gives a considerable amount of relief,fast.
You can also use fels-naptha soap to coat up a heavy layer on your skin before being exposed.Then just wash off afterwards.
I dont have any experience with that knotweed.Invasive stuff sure does suck :(