paint break on the doors?

[midniteblues]

my truck was pretty much slathered in flat black(like most of'em in pa) when i got it.
the po didnt do a great job on the doors and jams but from what i could tell there was a very soft paint break line on the doors between the interior and extieror color.
I would really like too duplicate this as close as i can.
painting is really not my thing and i dont know all the tricks on how too tape too acheive a "soft" line. please explain.

also if anybody has pics of a oe paint door latch area that would help.

awe crap i'm posting this in the wrong area