Fellow players, this may seem like an elementary question, but I've seen a few players in my area do this: They apply a few drops of valve oil in the leadpipe and then blow through the instrument before playing. This process is repeated after they are finished playing. I was told when you remove the pistons for oiling you run the risk of scratching the pistons. The players who oil their valves through the leadpipe say they have had no reason to remove the pistons for oiling. Does anyone else concur with this method to apply valve oil?