But if you really want to have fun with terraforming you should make Venus earth-like. I suggest an exciting starting point: build a solar shade at the Lagrange point and block the sun. That would eliminate most of the hard problems with Venus temporarily while we did whatever work is needed to get it spruced up. CO2 freezes to dry ice below -80C or so. You could let through just enough sunlight to get the atmosphere at a pressure humans can survive- then all we need is warm clothes and an oxygen tank.
Once Venus is in that state, the problem is simpler- how to get all the carbon and oxygen separated so that the carbon stays in some kind of solid form.
Oh, and we'll want to go get a load of hydrogen, likely from Jupiter, to mix with that Oxygen to form water. Your fleet of transports moving CO2 to Mars needs to make a detour on the way back.
Edit: fixed a word and also lol, just start with building a planet-sized solar shade, says some a-hole on the internet.