I have some cracks in the mortar on one of my outer walls - some years ago a burglar tried to prise the door open with a spade and cracked the mortar. Anyway, it’s time to fix this. I’m thinking that I can simply brush a dry cement and sand mix into the cracks and then wet the wall. Good idea? Bad idea? Should it be a 1:1 mix of cement and sand or a 1:4 mix?
The only real way to fix it is to chisel out the crack a bit, and force new mortar into the area. A grinder with a masonry blade will also work to enlarge the cracks if you don’t want to use a hand sledge and chisel.
I asked a couple of weeks ago about using Sackrete as mortar, and the unambiguous answer was concrete would not stick or hold up to supporting blocks. I assume this is also true for brick, and your use of the term cement is synonymous to concrete.
There exist narrow chisels (just the width of the mortar line) for gouging out the 'tween bricks section. Then use a “grease gun” to squeeze pre-made mortar into the gouged-out section.