Making good progress on potty training

I started letting the boy go naked a few weeks before we left for Japan. He was doing a great job of letting me know when he had to go pee with plenty of time for me to get him into the bathroom and onto the toilet. In the beginning I re-instituted the "Cars for dumpers" program which we had started during an earlier attempt at potty training. Basically any time he peed in the toilet he'd get another Thomas freight car, all of which I had purchased used off of ebay. He became so proficient with going that I was soon able to stop giving him any train cars as a reward; he was satisfied just with flushing the toilet himself and getting a high five.
And then we went to Japan. I was worried that all the progress we had made would be lost during our 10 days abroad, but there was no way we were going to attempt going without diapers while we were traveling. Fortunately he picked right back up where we left off once we returned home.
I admit that I ought to have checked out a potty training book from the library, but I just never get around to getting there so I have been winging it. During a trip to Target in search of a toddler harness and leash for our Japan trip, we bought a battery operated Bill engine. We bought it so that the boy and his best friend would stop fighting over the battery operated Henry engine. But then Mr. W had the good idea to save it for the "Cars for dumpers" program for a BM in the toilet. We used this as motivation before and after our vacation. He would talk about it all the time, but still wasn't ready to have a BM on the toilet.
I worried that he was stifling himself because I kept him bottomless all the time. One day last week he had to poo and kept asking for a diaper change because he wanted me to put a diaper on so he could poop in it. I remembered from my research on EC that we teach them to eliminate while covered up and then potty training is mostly teaching them to eliminate while uncovered. So I refused to put him in a diaper. But I knew he would still refuse to sit on the toilet. As a compromise I put a pre-fold diaper on the floor, sat him on it and told him to poop there. Begrudgingly he did. He was excited to "help" me dump it in the toilet and flush it down. But I had to explain that he still didn't get Bill Ben because he has to sit on the potty when he makes the poop too.
The next day he had to have a BM again; I could tell by his face, so I put him on the toilet. He was pissed at me and pitched such a fit! I gave up and we both went upstairs to play in the nursery. A few minutes later he told me he had to go. So I sat him down on the toilet to pee and before I knew it he made his poop face again. And then he pooped on the toilet!!! I was so excited! He got Bill Ben so he was excited too.
After that we had several days with no BMs. But he was doing such a great job letting me know in advance of having to pee that I decided to start taking him out on short errands with underwear on. No accidents. Although I admit that it is very hard to get him to go on other toilets, he seems to hold it until we get home. Unless of course I let him pee outside. He loves that. Perhaps a little too much.
I went out with a friend earlier this week and came home to discover that he had a BM on the toilet for Daddy. Inspired by the book Everyone Poops by Taro Gomi, he always used to say that he makes a mouse poop, Mommy makes a mouse poop, but Daddy makes an elephant poop. Always very funny. But with his BM in th toilet for Daddy he announced that he makes a Daddy poop. Apparently he wasn't kidding after holding it in for so many days. He also kicked Daddy out of the bathroom so he could move his bowel in private. I wonder why the same principal doesn't apply for me?
We have been happy with all the progress, so many eliminations in the toilet. So perhaps too ambitiously I decided to leave him in his training pants while we drove down to Hug Point on the coast yesterday. I hemmed and hawed over whether I ought to put him diapers for the ride down and back, figuring he'd be without while on the beach. He gives me enough advance notice that I thought I'd have time to pull over and let him out to pee on the side of the road. I stopped once at the drinking fountain on the way down and he very easily peed outside for me. On the way back he fell asleep before I could pull over. My mom wanted to go through the Dairy Queen drive through, but that woke him up. So I decided to go inside and put him on the toilet. It was a major battle with two separate attempts to get him on the toilet and two flat out fits. In the end I had him go outside beyond the parking lot. And then when we got home he had a BM in the toilet.
So far so good. (Although I worry it is too good to be true) We're hoping he is completely potty trained by the time we leave for Italy next month. I'm also crossing my fingers that we don't have a lot of regression when the baby comes.