Hi. I think this is just the airbrush pen “b) Airbrush Soft” or similar.
The trick is to apply it just a little. You’d have to experiment with size and pressure to get the right effect. If it’s not good, adjust the color a bit. Very often an almost white color works well. If the bloom effect is pronounced, you may need to tint it more. This should work well for small to medium objects.
Example, the sign board here - Layout study with Bocchi
What you tried to do with these cyan lights is a bit difficult. To get the right effect, you’d have to change the color of the surrounding metal first, as if the intense light is overriding it’s natural reddish color.
For bloom on large surfaces, like around the whole rim, probably a thick flat line that is then blurred with a very heavily Gaussian Blur filter may work. I haven’t experimented with this myself, however. With the effects sometimes less is more, but naturally it depends on the mood you’re going for!