Lime + sand + stones = wall

Our house and garden walls are all made out of local stones with a sand & lime mortar. The garden wall is in poor condition and my wife has had a go at repointing it. It's very easy in principle:

Hack out old mortar if it hasn't already gone.
Wet stones down so they aren't dry
mix NHL lime with sand and add just enough water to make a mortar
squish mortar into gaps between stones
partially allow to dry
brush of excess and use a stiff brush to tap into place
leave to cure (2-3 days)

The NHL lime is slower to set than Portland cement and not as strong but its easier to work with but slow going, it's taken her more than a week to do a few square metres of wall and we have hundreds to do...!