I'm telling you, calmine only drys out the skin, makes it more itchy.

Get Lanacane to control the itch, the less you itch the faster it will stop itching.
You are just at the tail end of beating it down for the summer. We had an ocean of it here.
Get Roundup, not the whimpy econo grade but the concentrate. It will set you back about $40 for a quart but that covers about two acres for a season. Follow the instructions, but make it
only double strength. So if it calls for 2 oz/gallon (I think,) use 4 oz/gallon - no more.
Spray it on the leaves early in the morning, just the leaves. It will be brown in two days, and gone for the summer. Next spring cut down the dead canes and treat any newbies.
The logic: Many people fear chemical treatments because they don't know how it works. If you spray only the leaves, the plant absorbs it like water. It travels throughout the plant and prevents it from creating clorophyl, and dies. Whole plant, roots and all, and it won't be back. If you only spray the leaves, by the time it kills the plant it degrades and doesn't poison the ground water. It's only dangerous if you a) over-medicate and b) spray it into the ground. Doesn't work that way anyway.
If you wait until it's too hot, the plants' "pores" start to close up to retain water, and it doesn't work as well. You have about three weeks to kill that crap off.
We're down to only a few spots here and there after 4 years of spring-early summer sprays.