Good ideas for potty training?

I have 2 1/2 year old and a 1 1/2 year old and I'd like to start potty training them both at the same time. My lil' girl is the younger and I heard that girls potty train easier than boys. We are trying the pull ups for our son but he's not exactly interested in the potty on a regular basis. He's used the potty twice to go poo but won't continue using it. i'm affraid to push him too hard and detour him from using the potty on his own. But he's so excited to wear "big boy underwear". Any ideas?