I have aluminum Venetian blinds on the windows in the rooms that get the most sun. (Plastic was cheaper, so not all the windows got them). I have one metal framed frosted glass door in the back room which I discovered got hotter than blazes, despite the cloth curtains I put on the inside. I decided I didn't need the light from it, so I taped aluminum foil over the glass. Made a BIG reduction in heat getting in.

In general, patch up all the small cracks you can, in walls and caulk around windows, and if you have unused rooms where you can shut the doors, don't try to cool them, also.

Think of your home as a spaceship and try to keep the void outside. :^)

(Open windows where I live just equalizes the heat and humidity, it's not an effective strategy when the outside is like a wet wool blanket. Open doors would lead to a house full of lizards, so that's not feasible for me either.)