IDK about poison ivy, but for automotive grease, Dawn Ultra works wonders even without a scrub.

Like my dad says, "you haven't been proper dirty till you've had to use Dawn as shampoo".

Brake dust, OTOH, now there you need to scrub, preferrably with a stiff nail brush.

Yes soap will get rid of Urushiol and some mechanical action is required, HOWEVER the last thing you want to do is weaken the skin and break it down with too vigorous a scrubbing. That will just facilitate penetration of the oil into the skin, and make you more vulnerable until your skin has repaired.

I get exposure to poison ivy on a regular basis but I know there's a 2h grace period in which I do all the yardwork around that stuff then jump in the shower. A normal shower takes care of it all.

I wrote this in another branch, but I should repeat it here: I've had total success by cleaning with naphtha soap after contact with poison ivy.