Brush the paint on. Done. Easy as pie. Hard to screw up. If you don't like
what you've done, just use some methylated spirits (hardware store) and a
clean cloth to wipe it off, then try again.

Use some methylated spirits and a cloth to clean off any surface oils
first.

Call your dealer (or maybe a BMW / Lexus / Mercedes dealer), and ask if they
have anyone that comes around once a week/month and does touchup work.
Usually dealers will have someone come by that does this type of work on
used cars on their lots to make them look nice for resale.  They also have
leather/vinyl/upholstery folks as well for future reference - can fix
cigarette burns, tears in seats, and the like.

When you call, see if you can get the repair companies actual phone number
and schedule the appointment through them.  If you have the dealer handle it
for you, they will of course markup the price for the exact same service
(around here anyway).

I've had a couple of rock dings painted out of my 02 TL-S bumper (plastic)
and hood (metal).  The guy I used actually mixes the paint on site to match
your car - he has a big book with paint codes/etc.  He then covers
everything except for the ding/scratch and airbrushes multiple layers until
the new paint is up to the level of the old paint, then does a quick spray
of clearcoat.  You can still see it, but it is MUCH less noticeable than if
you had just used the touchup paint and brush - I have a black car, and the
light has to be just right for me to notice.  If memory serves it was about
$50 for a half-dozen chips - each chip smaller then a pencil eraser.

By the way, I'm about 400 miles south of Pennsylvania.  :-)

- Mike