It is often a cause for debate with wallers whether to use mechanical assistance to strip down and prepare walls. For me, on the majority of jobs I like to see the stone as it passes through my hands. In this way, I am able to grade it, assess the stone and separate into copes, throughs and super special bits that you need when building...the get out of jail bits that at times you need. (it's a waller thing!)
Having said all of that there are also times when having a digger, driven by a competent (and this is key) driver can save days and days of work.
Recently I and a colleague have been preparing a site where we have had to move around 90m of wall. It needs rebuilding away from the tangled mass of tree roots that have now grown under the wall. In addition, cattle have been allowed to graze close to the wall and have eroded the soil leaving the wall almost appearing suspended in places.
So, to have hand stripped this out, carrying each stone down a bank and laying it out; plus turfing the new line of the wall and removing loose topsoil would have been a time-consuming job, probably taking two of us a week. Instead with the help of machinery and a skilled operator who also builds walls and therefore knows exactly what we need...we were left with a site ready to build in 2 days. Perfect!