I just open a word doc, and use MS Draw, believe it or not it is a very handy CAD program. I mostly use the Autoshape/Lines/"Polygon-S Sided Icon" and try to make as few points as possible getting a rough shape. The "magic" happens when you right click on the object you've roughed out and "Edit Points" is the option. When editing points you can move them anywhere, and if you right click a point, you can change its attributes, I like making a lot of corner points because it gives you these 2 little bug antennae you can manipulate to create whatever curve shape you want from the corner. Once you make a shape, you can "Format Autoshape" and hit Size tab to see how big it is out to 1/100th of an inch, on a 1" = 1' scale, that's a 1/8th of an inch resolution, that's close enough in my world. This is a good tool to make things to scale and correct proportions.
I have gotten the hang of it pretty well and can trace out a car in like 5 - 10 minutes to FlowSimulate. Then I take whatever drawing & photo thing I have and convert it to a .pdf, then Adobe lets me save it as a .jpeg. It took me about 30 minutes to create the cap line drawing above. I do have a talent, don't mean to brag, but I can think in 3D pretty well, so the above was done essentially free hand, I just manipulated the points til it looked right according to the image I have in my head.
I should probably take an hour or 2 in the next 2 weeks and organize my thoughts & techniques on using MS Draw into a guide for folks. As I say, it's about all you need for the stuff we do, and I think pretty much everyone has it.
Found this basic guide online:
SDSU Training Guide for Drawing Toolbar