Posted: 13/02/2014 at 23:32
You need to clear at least 1/2" (12mm) depth of soil from the joints or the pointing won't last long. The more earth you can remove from the joints, the longer the pointing will last. Blast it out with a pressure washer if you have one. Use a 3:1 sand to cement mix and keep it fairly dry so that when you take a handful and squeeze it together, it doesn't fall apart. Too wet a mix will stain the slabs. Good video here:
you can make a rounded tool for finishing it off out of an old bit of 15mm copper water pipe if you have any lying around. Best done when the surface of the slabs are dry to help prevent the mortar from staining them.