The Internet is truly an amazing thing. Even though I live in rural Oklahoma and can currently only get decent Internet via satellite and cellular (that's supposed to be about to change), not only am I able to purchase quality violin parts such as chin rests from the East Coast, and not only am I able to order materials such as strings and rosin handmade in Europe, online media has taught me so much so quickly in learning violin.
I'm sure to some people, using a pencil on the string grooves in the bridge and nut is a no-brainer. The same is probably true for using the tube that comes on your E string to keep the string from cutting into the bridge.
But to many people, this is not conventional wisdom. People deal with broken violin strings very regularly, whereas these things supposedly eliminate breaks almost entirely. Did you also know to lift your strings (minus the E, which does not need it in using the tube) gently and slightly up off the bridge, individually, after tuning? This allows the string tension to equally distribute itself on either side of the bridge, another important factor to keep strings from breaking. I'm glad to now know these things before buying the Larsen Il Cannone strings in a month or two as I plan to do… YouTube is a marvelous thing…