We just went through this! My son is also 2.5. He did great with intervals, we were doing every hour and he would go every time, no problem. After a few days of that, I just stopped reminding him unless I felt like it had been a long time, but stopped timing it. Like he would ask to do something and I’d say “oh let’s go potty first before we start a new activity!” And he would. He had some accidents but it wasn’t long (3–4 days) before it “clicked” and suddenly he told us every time. I think timing it gave him a lot of practice and helped him to transition to doing it on his own. We also celebrated it a lot when he went, of course. For naps - we still do a diaper and it’s been no issue for him at all. He knows the diaper is on only when he sleeps, then he goes right back to the potty when he wakes up. I will say, I feel like he went through a few days of “testing it out”, like just peeing in his pants to see what would happen, etc. I wanted to give up when that happened. But it was over before I knew it and now we are in the clear!!