For bug holes, sack rubbing is an effective method. A good mix for sack rubbing contains 1 part portland cement, 1 ½ to 2 parts fine sand, and enough water to produce a consistency between that of thick paint and masonry mortar. Form-time holes, because of their high depth-to-width ratio, should be filled by dry packing. Dry pack is a stiff sand-cement mortar with a low water content, which minimizes drying shrinkage and improves durability.
Before repairing honeycomb and larger surface voids, remove loose material within the voids using a light chipping hammer. Then trowel repair material into the void or use a small pneumatic mortar gun to apply a grout similar to hand-applied dry pack.