This is not an answer to your question. But I wanted to direct you to a talk I attended at Duke in 2013 at which Ben Brumfield gave a very strong overview of crowdsourcing.
I found it very useful and, though it's from a while ago, would recommend it for anyone who was thinking about undertaking a project and who could use a primer.
From the upload description "This talk will present an overview of the landscape of crowdsourced transcription: where it came from, who's doing it, and the kinds of contributions their volunteers make, followed by a discussion of motivation, participation, recruitment, and quality controls."
I came away from the talk with a good sense of how one might frame, organize, and then implement a crowdsourcing project.
On 5/25/17, 4:21 PM, "Code for Libraries on behalf of Eric Lease Morgan" <[log in to unmask] on behalf of [log in to unmask]> wrote:
Does anybody here have knowledge or experience regarding crowdsourcing transcription services?
Some of my day-to-day work revolves around a thing affectionately called the Catholic Portal.  The Portal is an alliance of members who provide access to rare an infrequently held materials of a Catholic nature. Many of our member organizations are tiny, really tiny, and consequently they do not have very many fiscal resources. On the other hand, they are very rich is primary source materials. As these materials get digitized, there is a need/desire to transcribe them. (OCR will not be an option.)
I was wondering, do any of you know of any services supporting the crowdsources of transcriptions, or maybe there is a piece of (open source) software allowing me to publicize things to transcribed, and then allowing somebody to actually do the work?
 Portal - http://catholicresearch.net