Second thought i'd make another my results are rubbish but if you take time you can get some cool grunge text
Here we will learn to make this :
Into this :
Step one : Creat your text you wanna add this effect to (try usin a bold font like i did wat was impact). put your blendin options on and stuff then rasterize
Step two : now click the eraser tool , then get a grunge brush and make it smaller like this
Step three : change the mode to pencil like this
Step four : now start clippin away the edges of the text with your small gruge eraser till you get something like this
and thats it your done now you can add it into a grungey sigor you can just use a grunge font lol
hope you followed
Enjoy