So with this in mind, how much should I bracket by?
I'd suggest that you look at the examples in the link I posted in post #69.
You will find that the more you do this, the more you will get a feel for when and how under what circumstances the levels of visible light - which the meter can see - and the levels of near-infrared light - which neither the meter nor your eye see very well - correspond.
And I second the recommendation for using an incident meter. If you don't have one of those, a reflected reading from a grey card or similar standard works as well.