The individuals that are experienced in making mock-ups to sell on GraphicRiver are the ones that are likely to provide the most accurate and detailed answers. However, it's unlikely anyone is going to link to, or give such a detailed response. The reason being, that induces unwanted competition (in the nicest possible way)
You're essentially asking "is anyone willing to tell me how I can steal their sales and subsequent market share?"
There was a similar topic on ThemeForest where someone was asking for a detailed guide for how to create a Wordpress theme. All authors were reluctant to give any reasonable response, for obvious reasons.
Sorry if this sounds a little dickhead-ish, I'm just trying to be open and honest. I guess as a generic response, the best method to use would be to simply purchase a few files and see how they have done it.