Raising damp on internal wall

[markslostmarbles]

Can i inject a chemical dpc cream into an internal wall, shared with my neighbour.
-i dont know the wall thickness.
-the floor is solid, conrete / screed?

so do i.........
-remove render/plaster 450mm above damp signs.
-drill through wall for injection nozzle.
-how high off kitchen floor? as low as possible at an angle down?
-pva the wall.
-re-render, paint.
-done?

have i missed anything?

thanks for all help.
mark