Wow, 2 1/2 for a boy is good. My main advice is to buy a bunch of underwear and some patience.
My son now 8 started just before his 3y birthday, my brother didn't care until 3 1/2.
With my brother, it was a simple matter of he just didn't see the point. However, as soon as you made a super cool toy the reward for staying clean, he never looked back.
My son, however wasn't so easily bribed. He got the pee thing down in 2 days. WooHoo!. Then he had an episode with an autoflush toilet wherein he almost fell in... and then he would refush to even go near the toilet. Moved his trainer to just outside the bathroom at home. When we went out, we would look for the manual flush or hold our hand over the autosensor.
We went through ALOT of underwear. There are just sometimes, like when you are out that putting the mess in the trash is just best. He has even gone without a few times, because we were out and ran out!
He doesn't eat fruits and veggies and that had a lot to do with it. It wouldn't be comfortable, or would take a long time, and he just wasn't going to deal with it. It took about 6 months for him to really get the poop concept.
Good luck
M.