Big +1 on hand oil... It works great...

Also, on old or really dry strops, you can lather up GLYCERIN soap (never tried/heard of anything else being used, and glycerin soaps work great) and lather that onto the strop, then let it dry overnight, and brush the crust off, then rub it with the palm of your hand a little... It works well, but adds a little draw, so be cautious when doing it