THe deep crystal polish is a glaze. When applied by hand, the only effect is that it "moisturises" the paint and makes it look deeper. That's it. It's an optional step if your paint is new. If your car is parked outside often and is a few years old, it's good to apply the deep crystal polish once in a while. If you have spare time, just give the polish a go and see if it is worth the time.I use Speed Glaze, which is a combo of both the deep crystal polish and scratchX.
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