Midnight Cowboy quote that I can't understand

In Midnight Cowboy, Dustin Hoffman's character (Ratso Rizzo) says:

"You can't scratch yourself without getting a bellybutton up the old kazoo there."

This was when he was talking about going to Florida, Miami Beach, and the ladies there. He was talking to a handsome man (Jon Voight), who was trying to be a hustler in New York but could not succeed.

Clearly I don't know the meaning of scratching or bellybutton, or how they can be related to each other, or I cannot find the logic by which to understand this sentence using my current knowledge of English.

Solution 1:

"You can't scratch yourself without getting a bellybutton up the old kazoo there." is "metaphorical slang". The picture behind is: If you want to scratch yourself, you have to move. If you do so, some part of your body will inevitably touch at least one body part of someone else. That is only the case if many people are around you. Bellybutton and kazoo as body parts represent the respective whole bodies. In the context of the intention of his friend to be a hustler, what Rico wants to say is probably "There are so many girls around that you can't fail".