John Fogerty of Creedance was asked how he got that rough vocal sound. He said he would go into the woods and scream as loud as he could till his voice roughed up. I would say this is not a good idea and will just lead to vocal chord damage. If its any help I think singing more from the back of yoir throat instead of deep down will help but again be careful. Sort of like when you first wake up and your voice isn't loose yet.
As most pro singers do just choose songs that fit your voice.