A lot of people have e-mailed me asking this question. I created each and every one of these drawings with Paint Shop Pro from Jasc Software. This is one of the most popular graphics programs in use today. While it does not have all of the features of the legendary Adobe Photoshop, it is getting closer and closer every year, at a fraction of the cost.
I have found Paint Shop Pro very easy to use, but the drawings can also be created with Microsoft Paint, the image-editing software that comes with Windows 95/98. Apple users most likely have a similar program built into their operating systems. The only drawback is that it is more difficult to save the images into usable Internet formats without destroying the quality of the image with these programs. Get Paint Shop Pro (or a similar program) if you're serious about it.
I start by closely examining photographs of the equipment I intend to draw. I need good broadside views of the equipment, and occasionally some close-up shots will help too. Sometimes I will resize the photograph to the same scale as my drawings to make sure I am making my cars and locomotives the proper length and height.
It can be quite tedious at times. Each drawing is done pixel by pixel, with careful color coordination, and some neat tricks to fool the eye into seeing "detail". Of all the advice I could give you, none is better than this: PRACTICE. It has taken me a very long time to get good at this, and I still go back and change my drawings from time to time when I figure out ways to improve them. As a matter of fact, my F59PHI's have all changed about 4 different times since I originally drew them, and I am just now becoming satisfied with them.
Is it frustrating? Often. But fun? Yes, almost always.