Creating a specular map using point lights? Im following a tutorial online (can't post it here its paid) and ive got myself stuck.

In the tutorial she says you need to create a secular map by making a black materiel then shining a point light and then baking the light information. 

Hers looks something like this 





I tried replicating the same effect, I have a Principled BSDF with black but I don't know how to bake it out so its just black and white. The only thing I can get working that exports the light information is Glossy but it leaves these purple and brown artifacts and I have no idea where its getting that.

Any help on how to fix this or get the same type of render results using a similar method?
I checked on youtube, and so far, I found this one :

https://www.youtube.com/watch?v=_PPTG1waeZ8