Bubbles are one of the things I prefer to do in postwork. There's heaps of brush sets available. These are the ones I use most often. Highly recommended.

www.brusheezy.com/Brushes/1283-Bubble-Brushes-for-Photoshop

Expert in computer code including, but not limited to, BTW; IIRC; IMHO; LMAO; BRB; OIC; ROFL; TTYL. Black belt in Google-fu.