re:  Part of a well done oil change is to pre fill the oil filter B4
installing it (~3/4 full for a Vanagon 'cuz of the angle)

Yes, I do this when I can, even though I know I don't need to.  The
filter on my wife's MB mounts completely upside down and then I
don't.  (Only a "drop" spills when I remove the filter and that's not
because it's empty--it's a cool system and I hate to think what would
happen if I used a Fr*m.)  Again regarding "air" in the system:  When
the oil light goes out or the oil pressure gage moves from zero, it's
gone.  Go for it.  More like 15 sec than 15 min.  More like 5 sec.