I think Chris has covered this quite a bit on the home etching side. Instant gratification that way.
If you know a design program, the other option is to draw the parts and send them to an etching house. It can take a month or more to get parts back, but it keeps the chemicals out of your house and the precision can be a little better. (Outie rivets too!)
Bob Knight would probably talk to you about custom etching if you use CorelDraw files. If you know a CAD program like AutoCad, then I can help you out through White City Lines. It's sometimes difficult to find an etching house that will handle small hobbyist orders. So, for awhile now I've been working with individuals and small manufacturers to combine orders and run parts through one of the big houses. If you can draw the parts and get them in the right format, I can proof the artwork and get you the parts.
As far as part design goes, the general rule of thumb is that nothing can be smaller than the thickness of the sheet you're etching. So, .010" brass sheet, the smallest hole you want to etch is .010" diameter, and the smallest line thickness (like the cross hatch for a screen or grill) is .010" wide.
Here's the guidelines for AutoCAD artwork:
http://www.whitecitylines.com/etchingguidelines.htmSample HO parts in Stainless Steel: