Hi becky
I can sort of get close but ist really a hit and miss thing and not really something thats easy to explain step by step. I keep trying to refine the process to make it more accessible but its difficult.
Basically you can use the art paint brush at varying widths and styles, transparency and colour to get a good look ..just experiment.
the other thought I had was to create the look in PS or PSE on a black background using a white brush or vice versa then pull that into DiP, delete the black and use teh white as an overlay, colouring as necessary. make sense?
I have also used photos and played with extracting parts. The attached screen shot is part of a paper I was working on. The base is a photo but to get it distressed I used a photo I took of bark, made it black and white, removed the black and was left with a scratch thing lol , ok that makes no sense. Here is a link to the full size paper
http://www.scrapbookbytes.com/galler...cat=500&page=1
If you are interested I can upload the scratch thing for you and whoever else to have a play with. Just vary the transparency or colour or size or whatever to suit.