Yes, getting to a brain is almost always harder than beating them.
My advice for Tucker: GRASS AND WATER! I used a Ludicolo and a Lapras to battle him, and it was over in four turns. He *Usually* Sends Swampert out first, so have a grass-type ready to counter. (Me: Ludicolo) If you're lucky like me, Swampert will try to use Counter on you. (Since you SHOULD be using grass-type attacks, this shouldn't be a problem) My Ludi's Giga Drain sent Swampert into the red with what probably was a little over 20 HP. Next turn, it was down for the count. He then sends out either Charizard (what he did to me) or Salamence. Lucky me had Ludicolo knowing Surf, so that brought Mr. Charizard into the red. Charizard got angry and KO'd Ludi with Aerial Ace after that. Enter my Lapras. Charizard uses Rock Slide. Lapras uses thunderbolt. Charizard dead. I win.
Since I had a Grass/Water, this was probably easier for me than it will be for you, considering most Grass-Types can't learn Surf or Ice Beam. (Which was in reserve in case Salamence popped out).