There isn't usually scenery under the layout (besides dust and cobwebs). But if you haven't pre-drilled a hole for the throw-bar before installing the turnout, that's a bit of a conundrum.
If you are using a Switch master type under table switch machine, it actually has a metal rod which comes up through a hole with a sleeve that you could drill between the ties and slip it from above into the turnout throw bar hole. That scenario would work pretty good and not involve any scenery disturbance in the force.
Follow the link to see pictures and diagrams of what I am talking about:
http://www.builders-in-scale.com/bis/sm/schm-1001.html
There may be other switch machines which work in a similar way where you don't have to have a hole drilled directly under the turnout throwbar.
On my future layout, I am planning on manually throwing most of my turnouts, but I probably will pre-drill a hole anyway, just to leave the door open for under table machines.
Rio Grande. The Action Road - Focus 1977-1983
There was this thread in here not long ago, talked about under bench work turnout control, you might look through it as much of what was discussed in here could be done with the scenery inplace, and not be to invasive.
http://cs.trains.com/mrr/f/11/t/273482.aspx
I don't know of any specific articles or videos.
You could also try the Search the Community box, on the right hand side.
Mike.
My You Tube
Has MR or MRVP ever covered adding under layout controls to turnouts after scenery is installed?
Thank you
DB