Earlier in the year, after being told numerous times that SketchUp was an immensely useful tool, I decided to spend some time getting to grips with it.
It is a very easy, intuitive program to use and is
FREE to download!
I won't go into details, but, I've built (still work in progress actually) some MC-1 roadways and vehicles for a strip I'm doing for Zarjaz.
huge 6317 x3342px zoom-able versionI also built a lawmaster a while ago... rookie mistakes have been including too much detail, because these are only intended as under-lays to work over in ink.
fly-around videoThe other massive, advantage is there is a whole
3D warehouse where you can download useful reference models that other people have built.
The value of the ability to move around a model and frame shots really can't be underestimated. I recently did a DPS for Murky Depths and built a very simple church and graveyard and used it to try out more dramatic compositions...

In short, I'd recommend this as a simple, quick and effective way to take the labour out of tricky perspectives, certainly for things you need to draw multiple times from lots of different angles...
To use the exported jpegs effectively as underlays you need to export at a fairly high resolution which can take time, and then also fiddle a bit in photoshop too before you really have the under-lay you need, but I still think it's still slightly quicker than constructing it with traditional perspective drawing techniques.
I'd be interested to see other people's screen grabs, should they decide to get to grips with SketchUp, hopefully, this thread would be a nice place to do that.