Let's see if i can be of any help.I teach the "raspy"singing style to most of my students as it seems to be pretty popular.
I think dispelling some of the myths about it will save you some grief and even physical damage!Here goes:
1.You can sing this style without destroying your voice.
2.It doesn't require you to drink,smoke,take heroin or be directly related to Tom Waits.
3.It is a technique like any other and can be taught.
4.Having a clean speaking/singing voice doesn't mean you can't do it.
5."pushing"your voice or using excessive volume is not neccesary.It's about tone.
6.It doesn't take alot of effort and shouldn't be done any harder than when you are trying to broadcast in a clear voice.
7.It's not supposed to hurt!
8.It's mostly psychological and is pretty easy once you get the basics of it.
I will be happy to give as much advice as i can,the only problem is that it's hard to teach without hearing the other person.
Explaining exactly how it is done is much harder than just imitating the sounds of the person teaching.After all it's the same way you learned to speak to begin with,it will be the way you learn the fastest.
Something to remember-a long time ago you were about a foot long and when you wanted something you belted out a scream that could peel the paint off the walls and could do it all night if you had to,and could wake up and scream all day long again.You didn't lose your voice then and now you've got much bigger lungs and a lifetime of frustration to fuel it!The ability is definetly there.
If you want to post specific questions or give some samples of your attempts and what blocks your hitting i can give you more direct help.Hope i can be of service to you.