Maybe my understanding of blinds is wrong, but the ones on my window get pretty close to completely dark. Add a decent curtain (with insulation and blackout) on the inside, and I can keep the flat comfortable passively.
Whatever else you do, close the damn windows and doors during the day, and fling them wide open as soon as its cooler.
Maybe this is a weird European thing, but my metal blinds are outside, so yes, they are very effective at reflecting radiated heat away. The triple glazing does a decent job blocking convected heat and last but not least good quality curtains to block any conducted heat that makes it through. It's never going to be 100%, but I'm confident it's 100% better than yoghurt!