Knock-down textured surface walls is a lot of work and detail for a garage wall. The rough surface can impede finding studs and dose not facilitate hanging fixtures to the wall. It serves no purpose here.
But if you need it for repairs here is what I have done. Don’t pay the $$ for the aerosol cans. They cover a small area and you cannot control the density of the texture.
My walls had large and heavy blotches. The aerosol cans could not match this. I used a natural sponge and premixed drywall plaster. Then you can control the texture by experimenting with adding water to the plaster (I used plaster straight from the premixed can) and different grades of sponges (your local Lowe’s has different grades of sponges in the paint dept.). Just dab the sponge into the plaster and then onto the wall. Let dry to a paste and use a large trowel for take down. The toweling motion should be arbitrary (not up/down or side to side). Shine a light parallel and on the surface of the wall to better see the texture. Some experimentation is required. It’s not hard.
Good luck
