Question about por-15 putty or filler

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My biggest concern with POR 15 is I've heard that it don't like other products over it. Such as other fillers,Primers or paints.I am going to need to prime (K36) seal and paint 2 stage. So far I'm leaning toward the JB Weld to for a 1'st coat let cure then scuff then a skim coat of metal to metal or even Kitty hair for any inconsistencies b-4 I prime.