[Captain Ahab Jr]

My house is lat 1700's and stone and I've repointed most of it inside and out

To remove the old mortar use a small pick and scrape out about an inch deep, brush out any loose stuff with a stiff brush (similar bristles to a hard yard broom) and then use a finer brush (similar bristles to a good house broom)

DON'T use a power washer as you'll just make a big wet mess and then have to wait days for it to dry out

A mix of 1 part lime, 1 part cement and 6 parts sand should be a good mortar mix. Just fill the joints to flush over flush with a small trowel, allow it to dry partially until its crumbly to touch.

To clean off the excess mortar, scrap any excess flush with the stone using your trowel and then wire brush diagonally across the joint. Do the same again use a softer brush to get rid of the wire brushing marks.