A doctor who works in free clinic in Bend that does anal cyst exams and then forgets to take his glove off, which he then uses to write with a pen, turn on/off the light, etc.
When having sexmissionary, you reach around and between your partners legs and wet your finger with pussy juice from her taint, you use this as lube and stick your finger in her asshole. you now have pussy-butt finger.