Do Not Read This Title

This weekend I get to make up some song lyrics. Fun. Not. Have no idea where to start either :|

"Riverman" seems to involve someone drowning or falling into a river.

"That's not 'Riverman', is it?" Matt asked.
Ash laughed. "A bit too prophetic?"
"I thought it might have been a suggestion on your part."
"That'd be more obvious."

"My Lady is a Laddy" is apparently for singing when you are drunk.

Ash did a repeat of the his chorus.
"Maybe we can offer you up as bait," Matt told him. "It's a ridiculous song anyway."

My main character, to quote another character in the book, can't open his mouth without a string of obscenities coming out. His friends aren't much better. They're crude, bitter, uneducated and, yes, they do have a limited vocabulary.

Obviously this in one area where written speech differs from the spoken word. Putting f*ck in front of every word doesn't work, even if that's how someone actually speaks, because swear words have more impact in print. Limiting it too once per sentence looks silly. It's too artificial. Not using any at all, in the case of these characters, just reads wrong.

I googled a bit to find out other people's thoughts. Not very useful. When it comes to swear words, it seems there are three approaches.

The first uses the idea that if swear words are used very lightly they have better shock value. I understand this. If a character who doesn't usually swear, or who uses mild curse words, suddenly comes out fuck or their culture's equivalent, then it has an impact. They're angry! They're upset! Whatever. Running alongside this idea is the common thought that overuse of curse words reduces their impact, dilutes them. Of course it does, and if you want the shock! effect, it's something to bear in mind. I'm not sure it's so appropriate to this situation.

The second type of discussion goes along the lines of "I don't use swear words in my writing and you don't have to either. Here's how!". Um, yes, there are many characters types who don't feel a need to swear. We know this. Now fuck off.

The third is don't actually use it. "Jill ran together a string of words that made all those around her blush." We can see how this would be a little difficult for a main character, yes?

I guess I shall have to pick up some books with crude, bitter, uneducated characters of limited vocabulary and see how they're handled. Suggestions?