Step 1
Tape a handful of matches to your piece of cardboard and dip them into the shellac. You don’t need to completely submerge the matches, as long as you get the match head and bit of the material nearby.
For the sake of being relatively scientific, lets say that at least 1/2″ of the match (including the match head) should be submerged into the shellac for at least 3 full seconds.