Surface colonization of venus is out of the question until we develop some means for reducing the planet's surface temps to something less than foundry levels.
Venus has the wonderful attribute of a very thick atmosphere containing carbon dioxide. Carbon is very useful as a construction material
in the form of nano-tubes which are naturally formed tubes of carbon and usually nothing else. These tubes are extremely versatile, extremely strong and durable. They atre also extremely lightweight.
The suggestion here is to deploy factories inside Venus' atmosphere which can take raw atmosphere, process out the sulfur and chlorine (which are then used to support the industrial operations on Mercury. . .) then break down the CO2. The carbon would be used to create carbon-based structural elements - including ultra-light fabric - which would then be used to assemble agiant belt over Venus' equator and extending north abnd south a considerable distance.
The giant belt - not to be confused with 'ring' - would shield about 50 percent or more of the sunlight. The remaining sunlight would result in about the same flux as Earth gets. Only the polar regions would actually get natural light, but that would be at an angle which would result in far less heating.
The simultaneous reduction of CO2 and solar flux to the surface would eventiually yield a cooler surface - though probably one still hotter than the sahara in high summer. Its a start.
The belt has much better dynamics than any free-orbit lagrange satellite. It is essentially spinning in orbit while gravitatioanally locked to Venus. The spin provides a crude but reliable means to stabilize the belt and, since it is constructed over time, it can be reliably monitored for proper positioning relative to Venus' surface, which it must never touch!! Any instability would be noted long before it became a threat to the planet.
The oxygen liberated from the CO2 would naturally be made available for air and water production. Forget oceans though. They would likely find their way into Venus' subterrains and the water would never be seen again. Besides, the high sulfur content of Venus' atmosphere indicates there is a lot of the stuff in the crust. Oceans might liberate the sulfur and create seas of suluric acid. Nice.
This concept is not about terraforming Venus in the usual sense, but just making it accessible for humans.