I'm using this: AccuTech Economy Pyrometer
Yes, you need a probe; the surface of the tire cools down too quickly.
After some more driving this weekend, I'm really liking the additional camber. The car feels a lot better when cornering at the limit, and the limit is definitely faster.
Do you know what your final camber measurements are for both front and rear? I wonder if increased negative rear camber adds to understeer.