Some people support putting adhesive tape on the outside of the accordion buttons.  However, if you have ever received an accordion that has been prepared that way, BEWARE.  Sometimes, the tape they use is so bad that, even tho it did the job of protecting the buttons, it will take forever to get the stickiness off the buttons.  Recently, I purchased an accordion that was prepared for shipping using this method and it took me an hour and a half to clean the 120 buttons.  The only way is to use the other method, where you open the bass panel and put the strip of cardboard in.  You have probably seen those instructions.  I have never had damage to an accordion that was prepared that way for shipping.  However, the sticky tape is DEFINITELY not the way to go.