My DD "can't see the forest" either, so it doesn't work to tell her that when she gets dressed she can go to _____. What DOES work lately is telling her that if she doesn't put on her pants she will go without pants or socks or whatever. Or to say "If you don't let me help you with your shirt then I will not help you with your shirt." And walk away. I know it sounds weird, but she can make the connection to immediate logical consequences where she cannot make it to something more distant, like the trip to the park. And, yes, I have brought her out to the car without various items of clothing on. It causes a riot, and then she begs to put them on, and it really didn't take more that a few times for her to learn that I'm not going to fight with her over this.
It sounds like you want to be really respectful to him and not force the issue, and I believe that honoring his body is really important. So I guess I would say to totally leave it alone if he resists unless there is a reason he has to get dressed. This morning, I held my son in bed when he was trying to get out and told him we weren't done with morning routine yet because I hadn't changed his shirt. Then I caught myself and realized, wait what is the big deal? So I told him if he wanted to wear his PJs to town that was fine with me, and he was thrilled. But if he is not wearing pants and we are going to town, then I do feel he has to get something on his legs, and I will say something like, "I do need to get something on you, so let's think of a way we can make it fun." So that he understands that it has to happen but that I'm working with him. Son kids are really sensitive to pressure and if you push they will push back, on principle. I was one of those kids, and now I have one of those kids, and it can be really exasperating. But finding a way to let them keep their dignity is important, or else they'll get it back with negative behaviors that help them feel powerful again. When I can stay calm about a boundary I'm setting it goes so much better. When I act out of anger, it's all over...so a lot of it for me is getting through my own emotional storms and then the answers just become obvious.
A couple more thoughts on helping them have their dignity but at the same time get something done (when absolutely necessary)...try to give him an out, like say, "Well we do need to get dressed before we go, but would you like to read a book first?" And if he says yes, then say, "Okay, but when we're done it's going to be time to get you dressed," and then do your best to stick to it, and say, "We agreed that you'd get dressed when we were done with the book, now should we do it this way or that way?" Basically, giving him as much choice as you can, but at the same time, making it clear that whatever the task is at hand needs to happen.