Having worked as a chemist for almost 30 years now, I won't argue with the
dangers of contacting hydrofluoric acid (HF), even in small quantities.  It
really is extremely dangerous.  I wonder, though, whether one is really
very likely to encounter it in burned polymers during automotive work. 
Many polymers contain fluorine and therefore would produce HF if burned,
Teflon being the most common.  Most cars contain them, this is not just a
vanagon issue.  But this has been true for years and I've never heard of HF
burns occuring among mechanics, even those who work on cars day in and day
out.  400 C is extremely hot, (752 F), probably not attained except in
fires.  I'd probably wear gloves if I were disassembling a burned vehicle
(but I'd do that anyway) but I doubt if this is an issue for routine
automotive work.

Bill