Analyzing and assessing your environment can be a daunting task. Don't be afraid to hire someone to assist in the process, especially if you're already overloaded with day-to-day duties—the money will be well spent. DBAs often work extra hours just to stay above water; an expectation from management that you can complete a consolidation assessment, analysis, and proposal in a short amount of time (which is usually how the request is made) is unrealistic.
Hiring someone to help with your consolidation project can have other benefits also. Someone from the outside might be able to gain access to resources such as application or business owners that a DBA doesn't typically have access to, giving the final analysis more points of information. In addition, an outside party is likely to be impartial and can be objective in creating the final document that specifies what you can consolidate and what must remain as a standalone installation.