As part of my parents' boathouse makeover, they had to tear down a bunch of cinder block walls in order to remove an unpermitted addition. You can see it was no small feat:
The demo involved breaking up the blocks and resulted in rough unfinished edges on the blocks they did want to leave standing:
For aesthetic reasons we decided to cap the blocks to give it a smooth finished edge. The easiest/fastest/cheapest solution to repairing the cinder block was using poured concrete and then painting the entire wall to mask the patch.
To do this, you can't just spread new concrete onto the old blocks like cake frosting. You won't be able to get a nice flat finish, and it won't adhere very well.
To attach the new concrete to the end of the wall, you need to use wall ties. The purpose of these metal straps is to provide a connection between your new concrete and the original wall. The straps help transfer the load and allows for lateral movement (so the new concrete doesn't peel away from the wall with settling or impact.)
For the best adhesion, you should wet down the surfaces which will come into contact with the new cement. You want it damp not wet. A hand held mister bottle works great. Using a trowel we filled the hole with the wet concrete, making sure the top was smooth:
After about 24 hours (a little more since we had high humidity) we removed the form and had a beautiful finished edge to our wall: