Potty training troubles?

My son is 2 1/2 and i'm finding it almost impossible to potty train. He won't sit on the potty long enough to even try. If i have him use a baby potty he thinks it's a game and won't do anything but try to play with it. I tried just putting him in pull ups doesn't help. My friend told me to put those training underwear on him and if he used the bathroom on himself he'd start to learn because he'd not like it. Well needless to say I don't think he cared. I am not surprised it's a hard process because my son is also not talking yet. He is smart, he knows what's going on, but some of the milestones are slow coming. Like he walked late too. He knows the sign language for potty but he does that then i sit him on the toilet and he'll start chanting "potty. Potty" shaking his hand like the sign language shows him but I'll sit him down and...nothing. I'm interested in seeing some of the answers for your question because I could use some pointers myself! Good luck to you!!