1) What are main step and sequence: (es. 1-Propose Topic 2-Attract expert 2-collect question
2) What are main tools to recruit Subject Matter Expert (channel to contact, incentives, ....)
LinkedIn can be a great way to find people. But building on LinkedIn is like building on quicksand. Your goal should be to build your own platform / venue and bring the conversation there.
Social media has its uses. But you should build your own business, your own brand -- not theirs. Ultimately LinkedIn or Facebook or Google Plus owns your members. They own your written content too.
LinkedIn in particular has some potentially fatal issues, to which management appears to be indifferent. Content is frequently deleted with no opportunity of recovery. Group managers (and now, it seems, even group members) can sabotage rivals -- in a single click preventing them from posting across all LinkedIn groups. With risks like these, you should build on your own soil.