Sand Filled Areas Smooth

working in this 1950s renovation we're doing a lot of sanding doing a lot of spackling and doing a lot of bondoing and the red stuff on the doors right here is bondo glazing putty and that's what we put on after spackle and sand that because it's harder than spackle it sands flatter and it gets rid of small imperfections that sparkle will not get rid of because it's too soft and it'll stand out so we use bondo now the bondo glazing putty is red