You may just want to go ahead and get a seat for the toilet. My son preferred the ones with handles, so he could steady himself, but avoid the ones with a spray protector, they can hurt little boys. One Step Ahead has a nice one with a built in step stool, it helps them be more independent.
Good luck as you start on this milestone! My son got interested in the potty right before he turned 2, and he only pooped himself 2 or 3 times over the next year - but it took OVER a year for him to get to the potty consistently to pee. Can I suggest that you skip pullups, and go straight from diapers to underwear? I wish I had done that with my son, the pullups just seem to confuse kids. Once we switched him to underwear, he stayed dry most of the day, it was just laziness because he knew he could pee in the pullup if he didn't feel like leaving his toys to go to the potty.