Ridge vent through the roof with a switch to pull cool night air into the attic in the summer.

Attic ventillation is good, I have two wind turbines on the house and one on the garage and an electric exhaust fan on the gable vent set to kick on at 100 F but it rarely runs.
I've been up in the attic in the middle of summer and while a tad uncomfortable, it's definately not unbearable.
That's another reason I question the need for the thermal barrier stuff.

On new construction around here, most are using Radiant Barrier.

Radiant Barrier reduces the emission of heat (Black body radiator) of the roof plywood, etc., into the attic. The foil stuff works really well and reduce the emission of roof heat into the attic by 95%. The spay stuff (basically silver paint) is about 75% effective.

R38 would be overkill for your place, as you can see from the chart. In my neck of the woods, both of these can reduce a house like mine from using $300 for A/C down to maybe $200. Of course to further reduce you need to look at the walls and the windows, not to mention sealing the bugger up.

Solar panels can also help reduce your roof heat load as long as there is an air gap between the panels and the roof.

Gary - Do y'all work in Houston or have affiliates in Houston?

if your elec. fan isn't kicking on at 100 degrees, then you don't need any of that stuff but an additional layer of insulation between r on the rafters. Don't spend your money on the spray. Sound like you need air movement within the house. Are the doors closed when the HVAC is on? if the answer is yes, how big are the gaps on the bottom of the doors?