This approach worked the best for me. At the moment I could name maybe 3 items in my whole wardrobe that bring me joy just like that.(For example a pair of wide fit high heels, whenever I see them I feel like smiling silly because I know I look great in them and they don't give my overly sensitive feet blisters, for me no blisters is pure joy)
However I could perfectly point out which of the many dark pants i had I really don't want to wear and would wear a different pair if possible. I had three pairs of short shorts, I gave away one that I couldn't stand how it looked on me in last years pictures and one that I always felt like pulling lower. I can't say the pair I left brings me joy, it is more like I felt bad when wearing the other two and I have no feelings either way about wearing this one and I had no real need to have three pairs just for the sake of having them. Same went for the dark pants I had accumulated through the years, I could very well do with just half of the amount. I kept a couple extras for weight fluctuations, but gave away all the ones that were just too short. Wearing too short pants makes me feel sloppy and makes me want to be home as soon as possible no matter what else I am wearing, so away they went to hopefully get to some shorter person in need of pants.
A trick I use is I have a neat box on a bookshelf near my wardrobe, when I take something to wear and I think something like "ugh, I'll wear anything but this" it goes in the box. Eventually I give the contents away or change my mind and pull something out before that. This is how I ended up with just three bras, however all of them fit correctly and instead of looking for a specific one I can now just grab whichever because I like all of them.
Instead of leaving only items that bring me joy, I tried to eliminate the items that bring me distress and just because some people declutter quickly in one go, doesn't mean it is or even has to be the right way for you. I have no idea if my examples help you any or not, but best of luck!