I Second the pam or WD-40 method. JUST DON"T FORGET TO WIPE IT OFF AFTER YOU GET THERE. Went to go grab hold of the tower for a board and almost killed myself.
For the speakers........plastic wrap works good.
Otherwise check out
www.Speakersox.com Great product and a great company with awesome customer service. Worth every penny if you ask me. I tow 200mi one way about every 2weeks at night with tons of bugs. When they get caked on either throw them in the machine of just take them off and dunk em in the lake for a short term solution. It easy to make your own covers if you have a sewing machine, but the Speaker Sox ones use a nice material that I couldn't find anywhere. Their fit is right on like a spandex type material that form fits to the speakers.