Ira Glass calls this the 'creative gap'
If you don't have time for the video, there is a nice poster that sums the advice up too.
This is the gap we all must face as creators, but luckily there is help out there to bridge it. If you sit around hoping divine intervention will do it for you, you're going to have a bad time. Instead, we have google.
If I wanted to draw something complex, say a helicopter, for example, I might do something like this...
That's all well and good if my intention was to make a comic 'icon' of a helicopter, but what if my purpose was to make something closer to reality? In that case I have a wider gap to bridge...
I could get an image from google image search.
And find things like this....
And if i'm lucky, it might be exactly what i'm looking for, in which case, I can trace it or copy it into my work. But comics are more complex than a one-off image. Many comics need the same object or location repeated many times from many different angles. That image above is great, but limits me to just one view. It would take a lot of searching and luck to get a range of views of the exact same helicopter... Luckily, google image search is not our only tool.
Google Sketchup is a free 3D modeling tool, for PC or Mac. In it you can make just about anything, but what we need is even easier.
When you open the program, there is a 'get models' button that will take you to an online warehouse of existing models.
Search for what you want and when you have found a likely model, you select 'no' when it asks if you want to load directly into sketchup. This will download the model file, and then you can open it up directly.
Now it's open, you can see how the model looks...
But for our purposes, lets change the rendering (the way it looks) to make it easier to copy.
First go and set the face style to monochrome.
Now set the edge style to 'edges'
Now your model looks like this... much easier to see the lines and shadows. Play with the 'orbit tool' and rotate around your model to get an angle you like.
Using the 'pan' tool (it looks like a hand) you can move the view to center the model.
And the 'zoom' tool (looks like a magnifying glass) can get your view closer or further away
Now we can go to 'file' and 'export' to save a 2d image of your view.
Once in word, this file can be printed, then you can trace or copy the relevant bits into your panels.
Doing this may seem like cheating, but it is the way artists have worked since antiquity.
This is an example of a 'camera obscura' which was a special room that projected a view onto a large piece of paper pinned to a wall for an artist to copy. This would then become the 'cartoon' from which they made their final artwork.
Closing the gap is the aim, use whatever tool you can to do so.