gentlemen, Tomorrow I'm gonna grind out about a 5/8" depth of mortar around the whole furnace chimney, so I can have the same color mortar all around......Since this is my first chimney mortar repair I have been on youtube trying to educate myself.....I bought a grout bag as it looks like it is the easiest way to go. My question is how thick should the mortar be? How long before I start pushing the mortar in with tool or stick? and when is the appropriate time to use a brush to get loose mortar off that may have fallen onto the bricks?