Cooling down Venus will probably be by far the most efficient method to start terraforming the planet because then you wouldn't have to deal with the high temperatures and pressures at its surface.
I've chosen the final temperature of -50⁰ C since that is just above the triple point temperature of CO2 where this gas could change into a liquid ocean and because at the same time the lowest possible atmospheric pressure could be reached at the surface of Maxwell Montes, with about 10 km elevation the highest area on Venus. (light-brown on the image below)
Taking into account the total liquid mass of CO2 in Venus' atmosphere at -50⁰ C, the total surface area of the planet and the liquid carbon density of 1155 kg/m³, a 835 m deep liquid CO2 ocean could span the planet if its surface had the same elevation everywhere. So the surface of that ocean would then be at +835 m elevation, but since 80 % of the topography is within 1 km of the median radius the actual elevation would be somewhat lower.
So from the ocean's surface at 7 bar air pressure to the Maxwell Montes plateau there's a difference of at least 1.93 scale heights, meaning the pressure on the plateau would be 6.89 less or 1.02 bar (1.01 atm.) !
By comparison, at -40⁰ C CO2 would become liquid at 11 bar, and the scaleheight at that temperature 4964 m, while the CO2 ocean surface would then be at a max. +821 m elevation.
Then from the ocean's surface to the Maxwell Montes plateau a difference of 1.85 scale heights turns out to be, meaning the pressure on the plateau would become 1.73 bar (1.71 atm.),
With such low temperatures the CO2 ocean could be covered by about a 1 cm thick layer of water ice from all the water in the present atmosphere since during the cooling period probably most of the precipitated water would have flown to the lowest regions.
But can it be calculated how long it would take for Venus to cool down to a -50⁰ C surface temperature when it would receive no sunlight anymore ?