might have to wait for someone better than me but I can suggest you can add and change the Bloom instance inside lighting and you can also have a billboard gui with an image of glare in the light object itself to give a glare effect to it with LightInfluence set to 0 (depend on whether you want it to get affected by light around it)
I think the way they do this is using a image with that shine looking thing (this)
Im 90% sure its an image and they use cframe.lookat with a part to make it look to you?