A frame challenge:
Why do you assume that the rotation rate of Venus needs to be changed to make it habitable?
The aim of terraforming a planet is to turn it into a "habitable planet for Man". In Habitable Planets for Man (1964) Stephen H. Dole discussed the properties of a planet habitable for humans.
On page 58 Dole wrote that:
From the standpoint of human habituation there are two limits related to rotation rate. for slow rotation rates a limit would be reached when daytime temperatures became excessively high in the low latitudes below a critical latitude and when nighttime temperatures became excessively low poleward from that same latitude, or when the light-darkness cycle becomes too slow for plants to live through the long hot days and long cold nights.
On page 60 Dole guess that the longest possible day for a human habitable planet might be 96 hours or 4 Earth days long.
Dole then goes on to discuss the special case of a tidally locked planet with a rotation rate equal to its orbital period, so one side always faces the star and one side always faces away from the star in eternal night. Dole decided that all the water and maybe atmosphere would probably freeze out on the dark side, leaving the planet waterless and maybe airless.
Astronomers for many years ruled out red dwarfs as potential abodes for life. Their small size (from 0.08 to 0.45 solar masses) means that their nuclear reactions proceed exceptionally slowly, and they emit very little light (from 3% of that produced by the Sun to as little as 0.01%). Any planet in orbit around a red dwarf would have to huddle very close to its parent star to attain Earth-like surface temperatures; from 0.3 AU (just inside the orbit of Mercury) for a star like Lacaille 8760, to as little as 0.032 AU for a star like Proxima Centauri (such a world would have a year lasting just 6.3 days). At those distances, the star's gravity would cause tidal locking. One side of the planet would eternally face the star, while the other would always face away from it. The only ways in which potential life could avoid either an inferno or a deep freeze would be if the planet had an atmosphere thick enough to transfer the star's heat from the day side to the night side, or if there was a gas giant in the habitable zone, with a habitable moon, which would be locked to the planet instead of the star, allowing a more even distribution of radiation over the planet. It was long assumed that such a thick atmosphere would prevent sunlight from reaching the surface in the first place, preventing photosynthesis.
This pessimism has been tempered by research. Studies by Robert Haberle and Manoj Joshi of NASA's Ames Research Center in California have shown that a planet's atmosphere (assuming it included greenhouse gases CO2 and H2O) need only be 100 millibars (0.10 atm), for the star's heat to be effectively carried to the night side. This is well within the levels required for photosynthesis, though water would still remain frozen on the dark side in some of their models. Martin Heath of Greenwich Community College, has shown that seawater, too, could be effectively circulated without freezing solid if the ocean basins were deep enough to allow free flow beneath the night side's ice cap. Further research—including a consideration of the amount of photosynthetically active radiation—suggested that tidally locked planets in red dwarf systems might at least be habitable for higher plants.
So if a tidally locked planet with eternal day on one side and eternal night on the other side might possibly have suitable temperatures for life if it has sufficient atmospheric and water circulation to equalize the temperatures between hemispheres, a planet with very long days and nights but less than eternal ones might also be able to have suitable temperatures for life.
If humans terraformed Venus they might possibly have to help the heat diffusion around the planet by building giant pipes and pumps to pump water between the hot and the cold sides of the planet. That would be a vast project, but almost infinitely smaller than trying to change the rotation rate of Venus.
And the might have to build their cities with super powerful heating and air conditioning systems to star warm in the coldest period of the night and cool in the hottest period of the day. But that would be almost infinitely less vast a project than trying to change the rotation rate of Venus.
The solar of day of Venus is 116.75 Earth days.
An annual plant is a plant that completes its life cycle, from germination to the production of seeds, within one growing season, and then dies. The length of growing seasons and period in which they take place vary according to geographical location, and may not correspond to the four traditional seasonal divisions of the year.
The growing season for annual plants on Venus might be one quarter to one half of the solar day of Venus, or about 29.1875 to 58.375 Earth days.
One seed-to-seed life cycle for an annual plant can occur in as little as a month in some species, though most last several months.
So some Earth annual plants might flourish in the long days on Venus, though many others might have to be genetically engineered to do so.
A perennial plant or simply perennial is a plant that lives more than two years.1 The term (per- + -ennial, "through the years") is often used to differentiate a plant from shorter-lived annuals and biennials. The term is also widely used to distinguish plants with little or no woody growth (secondary growth in girth) from trees and shrubs, which are also technically perennials.2
In temperate climate zones, many perennial plants shed their leaves and go domant during the winter months. And maybe they could react to the 58.375 day long nights on Venus like they were short winter season.
So I don't see any reason why the rotation rate of Venus would need to be changed to terraform it.