Potty Training is complete; Carson is now officially potty trainined!
So what worked? The biggest thing was getting advice from others. Initially we tried giving little snacks or treats each time that he used the bathroom. This failed miserably. Then we asked around. It was suggested that we make the bathroom 'his place'. We got big Pixar 'Cars' movie posters (which Carson loves) and hung them on the wall in each bathroom he used. We bought every kind of sticker that he might like. Each time he sat on the toilet, he could pick out a sticker and put it on the poster. He loved it.
He was only required to sit on the toilet for the sticker; he didn't have to actually 'go'. This helped motivate him -- no pressure.
There is this really expensive kids hand soap that foams up. Angela found a generic equivalent, and put a big Thomas the Train sticker on it to make it more fun.
To begin with, we told him to go every 45 minutes. We slowly expanded this until he started telling us that he needed to go.
After he seemed to have it down pretty well, we started weekly 'no-accident' charts. He got a sticker for each accident-free day. Once he had 6 stickers on the chart, he would get a prize the next day. First was a toy train, then a toy tractor, then the last two weeks the family went to ice-cream. These were a huge motivation for him.
It's been a month of accident-free days, so we are officially calling him Potty Trained.