You could apply the P21S after the #9 SMR, but I've found the wax application goes a little smoother (spreads easier) if I follow a SMR with the P21S GEPC. The P21S GEPC probably leaves behind some filler and/or spreader, which is compatable with the P21S wax formula, allowing for better coverage with less waste. I'm splitting hairs here though, and it is another step. I've heard some say that following #9 SMR (espescially when machine applied and worked in well) with the #7 Glaze has made little or no difference in appearance. Another use for a glaze or filler type product with some chemical cleaning proporties is to remove excess residue that some SMR's leave that won't (easily) come off with distilled water.
