My older son is/was a bit like that. He wasn't diagnosed yet when we were potty training him. Started around 2 1/2 and it didn't click with him until just days before his 4th birthday. In hindsight he either didn't feel the sensation of needing to go or didn't associate the sensation with needing to go. None of the tricks worked. He was night trained around 3 1/2 before he was day trained.

Early on, scheduling potty breaks is important. The "Before/after" rule works well. After he wakes up, before we go in the car, before getting in the bath, before going to bed. He's 10 now and is a lot better. He's good about eating a variety of food so constipation isn't an issue, but he doesn't wipe very well so has skid marks here and there. Up until he was 8-9, he would tell me that his rear end hurt--it was because he wasn't wiping well enough and he needed Desitin cream. We're getting him on a more frequent shower schedule so that helps too. Now and then he'll tell me that he needs new underwear because his are wet (damp really, just a few drops).

Maybe a timer would work at home. Set it for every couple of hours. Give reminders if you see him doing the pee-pee dance. Set a few times as Scheduled Bathroom Breaks.

My younger son will be 7 in September. He was easy to day train, right before his 3rd birthday. He'll get a few drops in his underwear now and then, but he's more because he doesn't want to stop playing. His issue is night time wetting. He's still in Pull-ups at night. It runs in my family so I'm thinking we have another couple of years of Pull-ups.

I don't make it a big deal. Just get them clean underwear and remind them about going to the bathroom more often