Exporting the carbon dioxide from the Venusian atmosphere is not the most effective way of terraforming the planet. It isn't realistic. This answer offers an alternative.
Fortunately, if you have this level of space technology there are better options. What you need to do is a three step process.
First, convert atmospheric CO2 into carbonate rocks. Most of Earth's CO2 is locked up in the form of carbonate rocks. To do this, just add water, Actually a ginormous amount of water. Fortunately, the solar system is chock-a-block with astronomical bodies full of water. Europa, Ganymede, Enceladus, and, possibly, even the dwarf planet Pluto. Instead of using Drainage ships to capture the Venusian atmosphere, use similar sized interplanetary vessels to import the equivalent of the Earth's oceans from Europa, Ganymede and etc. Dump the water in Venus' atmosphere and allow geochemistry to take its course. Thus, converting atmospheric CO2 into carbonate rocks.
Secondly, build a system of solettes as discussed in AndyD273's answer, to block out excess insolation (basically, sunlight) and allow the planet to cool down to acceptable temperatures. Once human settlers are living on an eventually habitable Venus this can be modulated down to Earthlike levels of solar radiation.
Thirdly, introduce photosynthetic organisms into the Venusian oceans and seas. These will convert the remaining CO2 into an oxygenated atmosphere. The original proposal by Carl Sagan, using algae, is now regarded as dubious science. However, a technological civilization capable of terraforming Venus will have more advanced biotechnology and will be capable of producing suitable organisms to do the job.
While the three-step process of terraforming is scientifically plausible, it should come with the following product warning.
Terraforming planets to human levels of habitability will usually geologically long periods of time.
This does mean millions of years. It's really a problem of scale. Easy to overlook the amount of change required on a planetary scale to terraform a planet. Don't be in a hurry to pack your bags for a move to Venus in the near future.