Whether you can use a brick rake or not will depend on the type of mortar you are trying to remove.
Portland cement-based mortar
If the mortar is a Portland cement-based mix, than you may need to use a power tool to remove the mortar – this type of mortar is most commonly used in buildings built after 1925 and can be incredibly tough.
Lime-based mortar
Soft, crumbly mortar is easily raked away with a brick rake – this tends to be lime-based mortars.
