FYI, I am very experienced with this very problem because until my recent move, my two dogs had free access to huge amounts of poison oak and I got it all over my face and whole body constantly for years. It was miserable.
Unfortunately, I have very bad news. There is nothing that helps. Read up on it on the internet. Sure, there are sites that are full of crap... but the real science of it is not debatable. Washing off the oil doesn't help. This is because the oil chemically bonds to the skin within seconds of contact and then it cannot be washed off. Sure, you can get rid of the excess residue, but the stuff that is effecting you is stuck and just has to run its course. There is one product on the market (check at the drug store). It's like $30 for an ounce. I can't remember what it's called, but it claimed to break the bonds with the skin and actually remove the problem. I have spend over $100 on the stuff with basically no relief. Poison Oak and Ivy (same oils) is amazing stuff. I literally have tried everything... the most sworn-by cure is hydrogen peroxide, dish detergent, and water. Trust me... doesn't work. But, try it if you like. At least that one's cheap.
My best advice is to take some benadryl, wait it out, and then work on figuring out how to avoid the problem. The benadryl will help reduce the itching because it is an allergic response, so an antihistimine does help while it is in your system, but you'll have to keep taking it every 4-6 hours and it'll probably make you pretty sleepy. I wish I had better news, but those are the facts. Everyone else might swear by a certain method or whatever, but I promise you you'll get limited if any results.... and the improvement is probably due more to time than any treatment.