How do you fix sticking wiper blade for Mercedes Benz 1997?

IS TIME FOR A REPLACEMENT OR MAKE SURE WHEN OPERATING HAVE THE WINDOW WET SO THEY WORK WITH OUT MAKING A NOISY My wiper blade seemed to be sticking and I replaced the blade.Nothing worked,until I sprayed some moisture repellant underneath the housing at the base of the wiper(underneath the black cover)I also smeared vaseline there with my finger.Haven't had a problem since