This started out such a cheap hobby! When my parents went at the end of October, they went down with enough quarters and pennies to press what we needed (anything released after June 2001). $100 each later...
They've replaced many of the penny machines at the hotels with new designs. In general, each hotel has 2 penny machines with 3 designs each. So that's 6 pennies, and then each hotel has a quarter. Some hotels have more like the Contemporary and the All-Stars. The parks also have gone wild on the quarter machines, and those are $1.25 each (very annoying because the DL machines are only $1 each).
The link that wparry gave is the most accurate list. Even if some of the designs are different, it is the best in terms of where to look for the machines. Like at the Grand Floridian you have to look around 1900 Park Fair, but then there are more pennies at their Bus Stop, and if you want the quarter you have to look at the monorail platform.
Here are a couple other links if you are curious about what coins were available in the past.
http://www.geocities.com/wdwpennies/
This one has quite a few pictures of variations
http://ecfanatic.homestead.com/wdw.html
As for cleaning, I used lots of things. Used to use Brasso, but when you are cleaning in volume it is a pain. Tried vinegar up until a non-pre 1982 got mixed in with a batch I was soaking, I got distracted so they sat overnight, it reacted with the zinc and if anyone did that wonderful little science experiment...the zinc part was slowly getting eaten away. Now I soak them in a bit of Weinmen's Instant Tarnish remover and then clean them with a bit of copper cleaner. Both of these are available at the grocery store, they're used for cleaning the bottom of copper pans.