Plastic playfield posts often get gunky residue on them that does not easily
wipe off. There are several ways to remove this stuff.
Some will come off just by running the posts through the dishwasher.
Most stuff will come off very well by hand using a playfield cleaner like
CP-100 or Wildcat #125. These cleaners were not designed for plastic parts
though and may cause some clouding--particularly the Wildcat.
Almost everything comes off very well by using Novus #2. But this is a long
tedious process since it requires carefully doing every post by hand.
If you're lazy and very patient and have lapidary equipment you can run them
through the tumblers for a day or two. This technique works very well for
metal posts and other metal playfield parts.
You may find that using an old toothbrush helps with getting to the small
crevasses where the dirt is difficult to reach.
If you have one of those troublesome posts that had an old rubber ring glue
itself to it, then you'll have to trim off the old rubber with a knife or
razor. The remainder can be removed using a number of different methods,
but the most popular is to ignore it, since it's covered by a new rubber