I'm repairing my garage for use as a winery. The walls have some dents and holes in them, looks like one of the previous owners probably drove the car into them or something. The house was built in 1947, but it looks like they may have done the garage interior later in the life of the home. I first thought the walls might be plaster on lathe or maybe stucco on metal mesh, but after digging in, it looks like it is some form of sheetrock, covered with a textured facing of some kind. Please refer to the picture. The drywall looks to be standard 3/8" stuff and the texture is about 1/8" thick on top of that. The finish is hard and gritty, like stucco. Can anyone tell me what this finish is, and what the best approach is for repairing these holes? I don't need the repairs to be perfect, but it would be nice to match them as close as possible. On first guess, I was going to square out the holes, replace with new 3/8" drywall, then make a mixture of joint compound and #30 silica sand to resurface. Thanks!