I use a Stofen and also bounce the flash (depending on the height of the place). I use flash on AV to fill shadows, on Manual otherwise & then play with the FEC to get it right.
I dont usually get the dark shadows under chins you were asking about.
Filters are a waste of time and will only reduce your IQ........ IMHO 
Why pay several thousand of $$ for a lens only to put a piece of glass on the front that costs a few hundred? Id recommend getting a hood for each of your lenses as these will protect you against a lot of potential bumps, scratches etc.
