This card, without all the bells and whistles, functions as a board wipe on a creature
The impression I got was that it was hard to sell things and virtually no vendor was buying anything
Of course, you need to pay for that 12 power somewhere , which has inspired Legacy decks that play Phyrexian Dreadnought to cheat it in on turn 2 with a Stifle
So I would keep Empoleon on the bench until the benches are pretty much full, then you can put Empoleon into the active Pokemon spot and use Attack Command which will be more effective early on since more Pokemon are in play, but as soon as you start knocking out your opponent's Pokemon you'll be able to do less and less damage with Attack Command, just make sure you have a full bench at all times when Empoleon is in the active Pokemon spot
I agree it is a bit of a pain searching for these
Celebrations: Classic Collection - Pokemon Card List and Prices