Ian, I have re-lumed hands before. I take the hands off and clean them out. In most cases I just poke the old stuff out. I water the lume down a little. I find that usually the lume tends to dry out from opening and closing the container, so a few drops of water may help thin it to the proper consistency, but you need to be careful not to make it too thin.
When I get the lume the right consistency, I put a small amount on a tooth pick and transfer it to the hand by rolling it onto the hand. If the lume is too watery, I'll wait till it dries and give a second coat, but usually I can get it right the first time.