What type of plants would work best?

The only thing I have found that will kill poison oak (which is what we have in the NWest) is a product called "Crossbow". It is expensive - about $30 a quart concentrate - & found at farm & garden type stores. It only takes 3 oz. to 1 gallon of spray, so it will last a long time. Some have used Roundup with good luck...but not me. Nothing "chokes" it out. I have seen 6 foot poison oak plants growing in the middle of a camellia bush. Be sure to cover up well, cover arms & legs & wear tall rubber boots if you have them. The resin can be removed with a product called Tecnu (available at most big box stores in the pharmacy section). Disinfect your garden tools with mineral spirits.