My house in 93 years old, and the chimney needs repointing. Chiseling out the old mortar is easy-but filling in the areas removed is a big job. My question:
-can you use that plastic mortar patch that comes in tubes? It is expensive, but easy to apply (you inject it from a caulking gun).
-if using regular mortar, can you squeeze it in from a pastry frosting bag?
Applying with a trowel seems like a hard way to do this. at any rate, access to my roof is easy, and it should be a two day job.
You may get away with it if your chimney has a liner, but being 93 years old I kind of doubt that you have one. What you want is called a grout bag, your masonry supplier should fix you up.