I had a block wall that had some missing cap blocks. I had to get rid of the old mortar first in order to replace them. I tried a sander, but it actually got so hot sparks were flying. I got a blade that was for cutting bricks, but it didn't attach to the sander. I finally gave up and just chizeled the old mortar off with a chizel and hammer. I tried to be careful, but chipped a few bricks in the process, but it got the job done. I don't know what mortar you should use, but I used cement to re-attach the cap blocks. Hopefully, someone else will have better suggestions.

"My skull feels like its on fire but I'm good." If you're done, sorry for the redundant reply. If you're still working on repairs, this is what I found useful. Tools: Brick hammer by Stanley with the new anti=vibe handles (makes a huge difference) This is an investment and costs 2x what a std hammer will. The head is a lot longer and narrower than a basic hammer. (1) 4" brick/mortar chisel; (1) 1-2" chisel. 5 gallon plastic bucket (usually free from restaurants or about $10 at store)Contractor gloves (fits well but hard to find small sizes, women's versions are too stupid)***Safety Glasses*** XFactor from OSH/HomeDepot are very comfortable and come in Sunglass or Clear indoors. Practice on practice blocks (already loose and lying about damaged) Gloves too! Soak new brick in bucket of water to start getting it wet. Chisel out damaged area. Clean up. Mix mortar and smooth in with trowel. Lay in new brick. Guide line helps. Line from brick is separated by folded width of $1 bill. Don't use $20s, they walk away (hehehe). That done, spray down. Spray 3 x a day while mortar cures. THis is very abbreviated. Please also consult different books and articles. Remember, SAFETY glasses!