Note that if you do dump Infrastructure onto Venus the population will be too busy on Agriculture and enviromental or Service Industries to actually do any work, I think you need to get the colony cost below 14 in order to get any manufacturing production.
Don't be tempted to mix infrastructure with orbital habitats, it'll drag down your productivity, for instance if you put habitats for 30 million onto venus, you'll get 58.4% productivity IE 17,520,000 workers. If you then dump 50'000 habitats onto the planet and add 20 million more population your productivity will drop to 12% which is only 6,250,000 workers. The smaller 30 million colony is more productive anyway.
To most cheaply terraform venus as discussed earlier in this thread build massive terraformers with a single habitat, you can construct them with industry instead of a shipyard, I aim for a total build cost approaching 3 times my yearly income then devote a large percentage of my industry towards the construction, also give it enough commercial engines to travel 200 km/s so it'll get into place in a month or so.
Keep in mind that with terraformers, habitats, fuel harvesters and mining modules only the first group to arrive at a colony actually counts towards production, if you add more to the existing task group they won't do anything. You need to move the whole task group away and then back for production to resume properly. A 5 second trip away and back will suffice.