If I were hiring, I'd skip the qualifications and ask for a prototype with every bid. The prototype in itself could be something very simple (I'd give examples but you haven't mentioned about what it is you want made).

Also, if you want good hackers, you must be willing to pay good money as well (and be sure to talk about that in your listing as well).

Edit: forgot to answer your question: yes, a decent outline should suffice most of the time.