this combo is based on the not letting your opponenet retreat.  To start off you have dark muk.  His pokemon power is " whenever dark muk is your active pokemon your opponent must pay 2 extra energies to retreat."  so even something with  a low retreat cost now has 2 or 3.  Pokemon like snorlax have 6.
Dark dugtrio doesn't add energies put inflicts damage.   his pokemon power is " whenever your opponent tries to retreat he/she must flip a coin.  if tails 20 damage is done to that pokemon."  pretty good
TR training gym adds another energy to both players retreat cost but dodrio is ther to erase that.
 
So with all these cards out your opponent must pay 3 extra energies and has a chance of doing 20 to the retreating pokemon, while you pay the normal amount.  also with dark muk in your opponents pokemon will automatically be poisoned but they can't easily retreat.  If you throw in some bosses ways to get dark muk and dark dugtrio out quick, you can stop them before they have a chance.
 
Scott adams elian_g_@hotmail.com