We had a redwood deck installed in the back yard in 1983, and for years, would treat it with a mixture of linseed oil and turpentine. We didn't do it every year, but we did treat it several times over the years. I don't recall ever using rags, always brushes and rollers. And I don't remember how we disposed of those brushes, probably let them dry and waited until trash morning to put them in the trash.
Last summer (8/07) I had the deck redone, and extended. The contractor used Choice Deck, which is like Trex, installed it over the existing redwood, because that deck was still very solid, and used new footings or whatever they are called, for the extension part. This stuff never has to be treated. The project wasn't cheap, but well worth it to me to not have to deal with treating the wood any more.
Do they still make turpentine? At the Fire Safe Council meeting tonight (which was very interesting, BTW), this issue was discussed. From what I gathered, now paint thinner is used instead of turpentine.