D.H.
I had two boys first and they were just 1 year apart. I can tell you what we did. First of all, I waited until they were exactly 2 years 6 months. They both trained within that week. First thing was I DID NOT have them stand up. (I was 29 when I had my first child and I had already heard all the stories about the mess that is in the bathroom from boys standing up even when they get older.) So, I taught my boys to sit down first...a few years later they stood up and there are no messes at all. Besides, with standing up..not only are they having to learn to potty, but learn to stand up and not relax. That's double work for them.
Next, I bought several hot wheel cars and put them in a bag and each time he went, he got to pick one. Since they are only $1 or less, it was cheap. This encouraged him/them to go. My second son did fine with just putting stickers on a piece of paper on the wall of the bathroom. No certain order, just sticking it anywhere. I think the toys were the best though. lol.
With my first son, he drank a LOT, so I had to actually use a timer to remind myself to get him to go. Eventually, the timer was expanded to a lengthier time...My second son could hold it forever, so I didn't have to do that with him.
They both wore underwear day and night from the first day of potty training on. They did fine at night as long as they went to the potty before they went to bed. If they fell asleep on the way home in the car or something, I'd put something on them. They did #2 within that week as well, but it probably took about 5 days.
I definitely wouldn't force the issue with making him sit down for a period of time. He needs positive reinforcement...something that would make him want to go to the potty. That's why I mentioned the toys. My boys loved and actually still love hot wheels. (They are now 9 and 10.)
I have a 2yo girl that is 2 years and 5 months exactly and honestly, I don't think that she is going to be ready at 2 years 6 months. I've heard that girls are ready sooner or easier...not this one! lol I've tried once already and she couldn't care less if she was in wet underwear or not. When that happens, they are NOT ready. So, I stopped it after two times in that very first day. I'm waiting longer. Seems like my boys were ready and she isn't. We'll see this next month.
But, I definitely wouldn't push at all if he just isn't ready. If he has had accidents in his underwear and doesn't like the feel of it...great! Keep trying. If you are using those glorified diapers, ditch them...pullups are only diapers. Yes, that means cleaning up the mess, but that also teaches them more quickly.
But remember, kids are usually ready between 2 and 4 years of age. No, none of us want to be changing diapers beyond 3 years of age, but sometimes that is the case. My sister has 5 children and she didn't even start any of her children potty training until they turned 3yo. I guess it was just easier for her that way.
Good luck!