You should get a good number of replies to your initial brief. As responses come in, review the comments you get and review the profiles of those that respond. In most cases, you can reject, make comments and organise these replies. Once you have selected a few potential developers or designers, it will be time to reply to their questions if they have any.

At this stage a designer or developer may want more information to give an accurate estimate on the final project cost and duration. Before sending on your Wireframes and Development Brief for clarity, ensure that they sign a Non-Disclosure Agreement (NDA). Use the attached file as an example of an NDA (remember that law differs from country to country, it may be worth investigating a bespoke NDA for your purposes.)

Once the NDA is signed and you have sent on the Development Brief and supporting documentation, your potential developer(s) will come back with an accurate budget and schedule. Make it clear that you intend for them to fill out the High Level Schedule in the Development Brief Document.

Make sure you are happy with the team's structure. Ask questions around testing (do they have a tester). If they are handling the design as well as development ensure you are happy with the look and feel of previous projects (is their designer credible). Establish who will be your main contact on their end.