I haven't treated my speedy with anything. I don't use mine in the rain, so it's never been wet. I also carry a plastic bag just in case.
Last week I met a girl who told me she's been taking hers out in the rain since she got it one year ago. The vachetta was really dark, so maybe it just ages it faster. It looked worn, which some people say the speedy should look "lived in". I think it can be broken in but still look good.