Pour ¼ cup powdered laundry detergent into a bowl. Add ½ cup hot water and stir to make a thick paste.
Dip a soft cloth into the detergent paste to scoop some out. Wipe down the interior of the dryer until it is clean.
Rinse the dryer with a clean, damp rag to remove the residue.
Clean the drum with a nonflammable, liquid household cleanser if it's still dirty or stained. Spray the cleanser onto a rag and scrub the inside of the dryer until it is clean. Rinse the dryer well with a clean, damp rag.
Put a load of towels in the dryer and let them tumble for about 20 minutes to dry the inside of the drum.