It can be risky to use a hairdryer to remove air bubbles from the resin. Hairdryers generally do not get hot enough to get rid of the air bubbles from your resin and may instead cover your art in dust and debris.  Most professionals wouldn't recommend using a hairdryer to remove any air bubbles in the resin. Using an actual lighter or blowtorch with a real flame will produce more heat and work much more efficiently in removing air bubbles from your resin.