I rarely use plastic cones, but when I do I wash them in really hot water and Cascade, then I wipe them down LIGHTLY with Dope thinner (not enough to melt/craze them), lightly sand with ultra fine sandpaper (600), then prime & paint.

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When in doubt, WHACK the GAS and DITCH the brake !!!

Yes, there is such a thing as NORMAL, if you have to ask what is "NORMAL" , you probably aren't !
Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY.
ALL systems are GO for MAYHEM, CHAOS, TURMOIL, FIASCOS, and HAVOC !