If a crayon has gone through a dryer cycle, you may have a mess on your hands.  The first step to cleaning it from the dryer is to remove any solid pieces stuck to the dryer drum.  Begin hardening the wax by placing a freezer bag of ice cubes over the crayon spot.  Once it grows hard and brittle, scrape it free from the drum with a butter knife.

Simple Soap and Water

Always begin with the least aggressive removal methods and work your way from there.  Take a clean cloth and dip it into warm sudsy water.  Wring the cloth thoroughly so that it is only damp when used inside of the dryer drum.  Begin scrubbing.  If that doesn't work. 

Non-flammable Cleaners

If you still see visible signs of the crayon, use a non-flammable household cleaner to remove it.  Read the packaging to ensure that the product you are using is non-flammable.  Apply the product directly to the cleaning cloth and rub on the spot.  Never spray or pour liquids directly into the dryer drum.  .  If that doesn't work. . .

Most Aggressive Measures

Spray a dab of W-D40 on a cloth and rub.  Wash the dryer thoroughly with warm soapy water to remove all residue.  Just to be safe, leave the dryer door open and allow it to ventilate for a few hours. 

Use harsh chemical cleaners as a last resort.  Most chemical cleaners are flammable and could cause the dryer to catch fire if all the residue has not been cleaned thoroughly.

Once the Stain is Gone

Whenever you have any type of stain in the dryer run a load of dry rags through before putting in any clothes to ensure that you have removed all of it.