I've never done a VSM without a team.  I don't think a VSM committed to paper by one person (or even a couple of folks) would be worth much.  You MUST get the folks who are directly involved in the process to map the process.  There's just no other way to do it. 

Who should be on the team?  Simply put, anybody (but not necessarily everybody) who is directly involved in carrying out the existing process.  Right now, I'm facilitating an Order Entry VSM team.  It comprises the customer service folks, their boss, and an inside sales person.  At my last client, I facilitated a couple of VSM's that focused on manufactured products.  The teams consisted of the production superintendent, the customer service manager, quality control, a shop floor supervisor, and the company president (he actually took the place of the purchasing director...it was a small company).  You get the idea.

Team membership should be between five and nine people, but there's no magic number here.  In general, fewer is easier to facilitate but get the people you need to have in the room into the room.

The main thing is...don't put a VSM together by yourself even if you go around and talk with people in the process.  Get them all into the room at the same time.

I generally schedule one or two half day sessions with the team to teach the basics of VSM and get a good start on the map.  If you just jump into weekly one-hour meetings, it can take forever to get a current state map drawn up.  Get that first map drawn up, then schedule weekly meetings to go over the data that's been gathered by team members and to refine the map.  So...one or two half-day sessions followed by weekly (no less than bi-weekly) meetings.  That's the format.