I keep a bottle of Oak-N-Ivy brand product called tecnu outdoor skin cleanser. If I have been in contact with the poison oak or ivy I wash the oil off with the tecnu. Works very well if used promptly.
I quite often have to throw away a perfectly good pair of leather gloves due to contamination of the oils. Small price to pay.
A huge plus one. I'm hyper allergic to Poison Oak/Ivy. The Tecnu works great.
Also you can pre-apply a product called Ivy Block, it works great as well. I wear disposal coveralls and throw away gloves anytime I know I'm going to be working around Poison Oak.
I have found using the the pre-block, the disposable clothes and then washing after with Tencu works great.