So, I decided to go with Urban Decay’s Optical Illusion (primer). I got a generous sample from Sephora & wore it several times, including this weekend when it was 94 & I had to be at an outdoors college graduation :( I'm not saying my makeup & face looked perfect, but that primer held up pretty well! & did very well in other (indoor) circumstances but still hot a hell weather. Thanks @MargeGunderson for the rec! I'm also liking the Smashbox Photo Finish Radiance Primer that I ordered, but will use it when it's not quite as freaking hot.