Conniec you said "I'm not sure what airway clearance is." That is most important to do after nebulizing. As you probably know the nebulizing is to loosen the mucus and after that it is important to do Air Way Clearance. There are several things to do under the category of air way clearance such as the breathing techniques, postural drainage, percussion clapping etc. and the important technique of huff coughing. The breathing techniques are to help get air behind the mucus and the huff cough (not a regular cough) to help get it up and out of the lungs.
By now after reading Sueinmn post you may have googled Air Way Clearance Methods.
Barbara