If you are in dire need of multiple proxies and you don't want to write them out, go to http://magiccards.info/
There is a link on each card's page for 1, 2, 3, or 4 proxies. Wouldn't hurt to have this as a site feature here.
However, for the purposes of testing versus competitive decks, here is what I used to do: Get a 12 pack of colored pencils or markers that don't smudge, and a pack of 3x5 index cards. Print up your decklists for the decks you want to run against, and split the 3x5 cards so that they be come 3x2.5. Then, simply write the card names on the index cards, one per card, one color per cardlist, until you are done. Lastly, sleeve them with a backwards land or something, and then you have a pile of 60 cards that represents anywhere from 3 to 8 decks for solo playtesting.