J.,
That's a great start! It's how we started too, only my son wouldn't go #2! He showed some interest, but I wasn't very consistent with him b/c of life - 4 yr. old daughter and being very pregnant with #3!! Eventually he was telling us more and more. Then I stopped b/c of giving birth - but he kept going b/c he wanted to!!! Before I knew it we went straight to underwear, had a few accidents, changed a few bed sheets, but he's potty trained!! Best thing ever, unless I'm feeding the baby in public - then I'm in a bind! ;)
I would suggest you ask him about every half hour. And I would suggest NOT going to pull-ups b/c they're expensive and confuse the child. Just my two cents! Good luck.
D.