If you apply materials that are not meant to be used together you could greatly shorten the life of your finish. We recently had a Mercedes come in with clear peeling off the front bumper and we were able to strip most of the rest of the clear off by pressing packing tape on top then pulling it off slowly. This is a lot easier and yields a more consistent surface than trying to sand off the clear.
If you use a base and a clear in the manor that the paint manfacturer recommends you have a much better chance that you won't face this problem down the road on cars that you've refinished. Almost all painting looks good as soon as it's completed but better paint products (and methods) tend to make the finish last a lot longer.
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