Training is almost always the answer but sometimes you just need strategy. If I mess up the first time, I always plan differently and use new tactics the second.
Oh them. Liza and Tate I think it was, a lot of people seem to have trouble with them but most times I've fought them I just surfed them out of my way. I've also been going through the game with the Macho Brace equipped, if you're familiar with the game dynamics, it doubles the amount of EV's my team get.
Basically, it makes them stronger than Pokemon at my level without it. I'm sure I'll be fine.
I've just reached Lilycove city, with a team consisting of Marshtomp, Swellow, Lairon, Kadabra and Manectric. And a Zigzagoon but only as a HM slave, not part of my main team.