Squint like you're paying attention.

Had a college professor who got his Doctorate(In Psychiatrics no less)had to work to feed his family, was a bag boy at a grocery chain. Hated it. He'ld carry the groceries out and load them in the customer's vehicle, and with all the innocence his face could muster he would say:
"F--- you very much". Said if they did a double take, he would get the stupidest smile he could find for them.

There is a way, be creative.