Complex sentence: Fleer began marketing the new gum as "Dubble Bubble" and Diemer himself taught salesmen how to blow bubbles as a selling point for the gum, helping them to demonstrate how Dubble Bubble differed from all other chewing gums.
Split into simpler sentences: Fleer began marketing the new gum as "Dubble Bubble" and Diemer himself taught salesmen to blow bubbles. This helped them to demonstrate how Dubble Bubble differed from all other chewing gums.